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"APPLICATIONS OF ACCELERATORS" - GREG NORTON

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MCILWAIN: What size beam spots can you get on these 10 eV resolution beams for ion implantation, so forth, a small beam?

NORTON: When you do ion implantation you really don't care about the actual beam size. Typical implanters have a one centimeter diameter after scan. However. if you want a very small beam, as in microprobe then I would expect the beam energy to be very stable. However, I am not an expert in this field . People at the University of Melbourne and the University of Oxford are recognized as the world’s best. These groups typically report a half micron beam spot in the 100’s of picoamp range. But for single event upset, which is what the University of North Texas people are doing, you are counting particles per second and energy resolution is not a concern. Howevber, there is no good standard for measuring microprobe beam diameters.

Frank Watt, who is now at Singapore, gave a very good talk at the Denton Conference last fall. He bemoaned this very fact. People keep discussing diameters without defining the term.

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"INDUSTRIAL CLOSED LOOP WATER SYSTEMS" - ROBERT DOWNEY

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McKAY: I'm interested in your comments on the D-I system. I'll briefly describe our system. It's a system that has some stainless in it, some copper, aluminum. It's a D-I system, it's kept under nitrogen so the oxygen is relatively low. Closed loop and there is five hundred _________ of various components in there. And we have had to clean it and have seen a black crud, which I think, comes from copper. How would these soluble oils and triazoles work in a case like that, fourteen Meg water?

DOWNEY: Okay. Well, one of the first things that I would recommend doing is whenever you do something like this you want to make sure that black crud is copper. Okay. There is nothing worse than misdiagnosing a situation. Usually even if you just have a teaspoon or a tablespoon of that stuff you can send it through your vendor to a lab and get it analyzed. I will always recommend that because it's not worth thinking that it's one thing and mistreating it. Because if you think it's copper and really it turns out to be iron from the stainless steel you're going to have a big difference in how you one, clean it up and two, how you treat it. So, I recommend that as step one. Step two would be once that you've determined what it is, determine what it would take. Let's say you're getting some copper corrosion. There are two things that have to be done. One is how are we going to protect that copper without compromising the integrity of the system, or the performance of the system. And that can be done in one of two ways. If the performance criteria are extremely low as far as the purity of the water, so much so that you don't want to risk having periodic editions of chemicals to be made up, let's say a polytriazole, what you might consider doing is start up the system and add a dosage of polytriazole to the system. And you can work with your vendor to calculate how much you will need. That can be measured and tested for. And let's say you're off line. You put in that polytriazole, and let's say you put it in, and the minute you put it in you're going to measure ten parts per million (10 ppm) of that stuff. Polytriazole takes time to bond to the copper. So if you test everyday, polytriazole, you will see it go down to nine, go down to eight, go down to seven, go down to six, go down to five, go down to two, go down to one, go down to zero. Now, you've got no residual but you know that it's bonded. So, you might say let's add a little more, put in five more parts per million (5 ppm) and it goes down to four, goes down to three, goes down to two, stays at two, stays at two, stays at two. All right. Now, you've got a two part per million (2 ppm) residual which has very little effect on your overall conductivity, would add maybe two to four micromhos of conductivity at the most, which I don't -- I think most magnet -- I can't say. They all have different tolerances. I know usually we try to keep it two hundred (200) or less. Some systems you need a higher purity than that, so I can't tell you. But what you do is add to it and get the minimum amount of polytriazole in there and then test once a month, and just make sure, yeah, I've still got that two part per million (ppm) residual in there. Because that's the little bit that's floating around in the water and hasn't bonded. And then you've got a little so if you lose a little water, there is a little in there to go in and bond. So you can do that. So, I think that's kind of the safe method of protecting the copper with the polytriazole, and it's the best way to get, because when you have protection you minimize the potential impact, any negative impacts on the conductivity. Does that make sense?

McKAY: Yes, might have to run it down so we run down to zero?

DOWNEY: You might. You might want to run it down to zero.

McKAY: Fourteen Meg water or better.

DOWNEY: Yeah. So, you might have to run down to zero, that very -- well, at least you'll have some protection for copper, and it might not be perfect but some is better than nothing. And the thing I'd recommend after that, which I'm going to slide on, none of you have done, is the measuring corrosion rates, with corrosion coupons. Any of you do that here on your water systems? This is the second thing because it's great to do stuff, but you've got to monitor performance. And if you put a coupon into the system, they're small three inch by three eighth (3x3/8") pieces of metal. This is an example of mild steel. It will be clean at first and then as it corrodes it will get dirty or it will gets the iron oxide on it. You will send it to the lab, they'll scrape off the iron oxide, and they'll give you a report and say your corrosion rate is is point eight mils per year, and you can use that against industry standards to tell how well your system is protected. And so for copper you want to be point one (.1) mils per year or less. And if you put in your polytriazole and your copper rates a point five (.5) -- it's not good. But if they are point one (.1) or less than point one (.1), you know that you're adequately protected. So, I'd say the key thing after doing anything is how am I going to monitor that. And usually that's set up just by a small bypass. You bypass a little water through this rack and you put those coupons in there so you've always got water flowing across a little PVC thing like that, two hundred fifty bucks ($250) is all it costs. Each analysis, people normally analyze quarterly. Quarterly analysis once every ninety (90) to a hundred twenty (120) days.

CARTER: Does this polytriazole affect PVC piping or any other insolating piping?

DOWNEY: Oh, as far as negative effects?

CARTER: Yeah.

DOWNEY: What are the negative effects of putting a polytriazole in your system? No negative effects on any of the metals, very commonly used in all water systems. No negative effects that the PVC will soften. It does not provide a food source for micro-organisms, although it's an organic it's not one they like to eat, okay. So, there is very little negative, what you can't say for all treatments. If you put nitrite in your system, bugs love nitrite because it's nitrogen, and they will consume it like crazy and grow. So -- but the polytriazoles -- now the oils, on the other hand, do have a negative and that oil is a wonderful hydrocarbon nutrient for bacteria. So, if you have a system with a lot of metal in it and you need to put insoluble oil you're going to have to very closely watch your bug counts, because you now have a nutrient in that system which is very tasty for all these organisms and they will consume it and will grow. That's the negative part to the oils, so that's a good question about the negative parts. Yes.

JOSHI: Will you discuss the scaling problem which occurs in the properties in the magnet, scaling problem or --

DOWNEY: Okay. Scaling problem; what does the deposit look like? Is it white or brown or --

JOSHI: It's sort of a white.

DOWNEY: Again, it might look like scale but it might be aluminum oxide. It might be zinc oxide. It could be a lot of different things. My suggestion would be, one, take that and have it sent in and find out what it is, if it's calcium or magnesium, then, yes, it is a scaling problem. And the primary recommendation, really, if you need to keep conductivity down is demineralize your water. But if you're putting demineralized water in I doubt very strongly that that is calcium or magnesium unless your demineralizer is not working well. In most cases it's some kind of oxide, either an aluminum oxide. It could be a zinc oxide, maybe if you've got some galvanized piping in there somewhere. Those are primarily the two that will give you kind of a whitish look. But I would have it analyzed first and then approach it to find out what it is.

MUELLER: You have defined a closed loop systems being closed to the air.

DOWNEY: Right.

MUELLER: In our system the reserve water tanks that the pumps are on have vent pipes on the top that are open to the air,-- what effect is that going to have on the system and what can be done about it, if anything?

DOWNEY: Okay. That's a real good question. It's almost what we might call a thermal storage system where you're open to the air. There are four things that impact corrosion and -- well, let me put it this way. Number one, if you're open to the air what are you going to get more of in the water?

MUELLER: Oxygen.

DOWNEY: Oxygen. So, you're going to have higher corrosion rates without a doubt. You're going to have more carbon dioxide in there. It's going to tend to want to push your pH down so, number one you're going to have more corrosive water. That's the one problem. What I really find in most open systems, they actually have more microbio problems because one; oxygen is a nutrient that bugs need to grow. If you have a very tight closed loop system with very little oxygen the bugs do not have enough oxygen to really grow. Once you open that you have all this oxygen, bugs love it, grow like crazy. So you get more microbiological problems in an open system. And those will result in the microbiological corrosion problems, the slime problems. So, you generate problems; you have a higher corrosion rate, more microbiological problems. You're going to have to pay closer attention to trying to fix those problems. And it's kind of hard to do because since it's open you can say, well, I'll degasify the water. You're just always going to be adding more in it when it comes in. So, the nitrogen blanketing idea that somebody talked about, that's the idea. Go from the concept to root cause, how do we fix the problem, is there a way that I can keep this air out of the system. Okay. But treatment for that type of system is definitely far different from some of things I talked about here.

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"THE PROBLEM OF BUILDINGS FOR VERTICAL TYPE TANDEM ACCELERATORS" - CHUICHIRO NAKANO

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BERNERS: Do you see a regular change in transmission from morning to afternoon to nighttime and to morning and afternoon and nighttime?

(Put up a chart.)

NAKANO: You said (deferring to another man) did I measure the transmission of the change of the transmission?

HATORI: We haven't measured continuing transmission yet, but three years ago, we sort of using the old radius, the AMS measurement, so we have measured the current of the stabilizer tube and then, for example, couple to fourteen (14) days. _______ Fourteen (14) measure _______ fourteen (14) measure, end of ______. In-between the stable -- the project I called the stable istops and fixed position, so about ten (10) meter beam line, some that if the transmission change of transmission of the 10th, the project of it change, but the _______ stations so far from the _________ station. So, the transmission and some other item out of transmission for the other item also change air independently, I think, so -- and then the data, the other job difference from outside has experience of the __________ detection rate and it's just so, and they have experienced the data change. And so they think they try to measure first the temperature, and temperature with everything.

BERNERS: Okay. Thank you.

ROBERTS: It was probably on your graphs but it was hard for me to pull this out. You have the tandem sitting here and then you have the ion source on the fourth or fifth floor. What is the largest maximum relative motion you've seen between those two? I mean, I see tilt in terms of millimeter per meter but give me a feel for absolute value of movement, okay. This is the guy who was answering before.

HATORI: This data will measure, not so hot in winter -- from December to May. But, in this order we have a chance to readministration we try to pass the beam to accelerator. And the position of the accelerator, we have a beam profile monitor. And we haven't the change of transmission yet, however we could movement of the beam by using the beam profile monitor. And it was very hot day, so we start the beam transport in the early morning, and in the evening, we measure it. The beam position is about two millimeters (2 mm) move, so the tilt is larger than data.

(Indicating chart.)

ROBERTS: Okay.

NAKANO: So about fifteen millimeters (15 mm) apart, after through the fifty (50) meters, the beam position change about two meters or three meters.

CARTER: Does the building have any special foundation or construction, i.e., earthquake protection or some sort of special movement control?

HATORI: _________________ of movement, for example, in case of -- so we have to take care of earth- -- big earthquake, being from Tokyo, we have never been able to take care of earthquake. We have never took care of earthquake, so this building on this campus, maybe okay to strain of ______________. So in this year, the COVAT, COVAT was after great big earthquake, but if the people, if we had same amount of magnification, may be down.

ROBERTS: Yes.

NORTON: This building is a rather old one, poured concrete tower, so it may not meet the present earthquake standards. That means the building may not have a very deep strong foundation. However, there is no accelerator column isolation like you found with the 20UR at JAERI Tokai. Therefore, if they had an earthquake similar to Kobe, I suspect there would be severe cracking and other minor damage.

CARTER: So, the fact that it was special didn't have anything to do with momentum.

_

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"AN UPDATE ON THE OAK RIDGE RADIOACTIVE ION BEAM FACILITY" - MARTHA MEIGS

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McKAY: Martha, you said there was a type of control knob for VISTA that you would definitely not recommend?

MEIGS: It's made by HiTek.

McKAY: Uh-oh!

MIEGS: I'm sorry. The reason I don't recommend it is because I am used to the kind that we have, that you can assign to anything in the entire system. The way they have theirs interfaced, you have a list and you step through it. We have a good design and all you have to do is interface it through CAMAC to the VISTA control system. We were very lucky this last year, we got to hire a software person for the accelerator system, so we believe that we can use our very good design.

McKAY: I think I know which brand we bought.

MEIGS: Oh, okay, whoops.

LAMM: Can you tell me something about the charge exchange cell on the ion source?

MEIGS: Not much. But I believe it's a re-circulating cesium charge exchange. That's as much as I know, I'm sorry.

WESTERFELDT: The vacuum system on the target platform, what kind of pumping do you use?

MEIGS: We use turbo pumps.

WESTERFELDT: And are the controllers on the deck or are they --

MEIGS: The controllers are on the electronic platform, definitely.

GRIFFIN: Who rebuilt your coils for your inflection magnet?

MEIGS: We, of course, go out on bids, and the low bid was Walker Scientific. Worcester, I believe is the way you say it, Massachusetts.

MR. ______: Wor-ces-ter.

MEIGS: That's the way I said it before. I was told by the receptionist not to do that. They did a good job and we had to stay on them. There was a long time delay, and the real problem is, they don't do scientific magnets much. They're a big business, and don't laugh, for junkyard magnets. I mean, seriously, they do millions of dollars in junkyard magnets. So, they were not as responsive for a small thirty thousand dollars ($30,000) project for a scientific magnet, and we, of course, had to have much more stringent specifications and testing than your basic junkyard magnet does.

GRIFFIN: So it costs about thirty thousand dollars ($30,000)?

MEIGS: I believe that's right. I'd have to check. I believe that's about right.

HATORI: Why is it you generate things as by using the spallation reaction and by using the iso type separator, the extractor? Extractor is top how -- how should I --

MR. ________: What is the half life?

MEIGS: Oh, okay. We're looking at half lives between the shortest we can get through, so --

HATORI: Maybe in dictation -- it's dictation except how -- how long does it take to extract?

MEIGS: How long does it take? That's a million dollar question. That's something that's kind of the real black magic in this whole thing, I guess it's black chemistry, I don't know. But it certainly depends on sticking times in the ion source, it depends on the diffusion through the target. There are several ways that are being looked at and Gerald Alton who works in our lab is, I guess, in South Africa -- I guess that conference is still going on in South Africa, looks at that sort of thing. And we don't know yet how long the half-life has to be. However, right now we're not going for really long half life things because we don't want to activate anything in the tandem.

HATORI: I think it is easy to extract by ______________.

MEIGS: We only use fusion reaction, the p,n reaction.

HATORI: No, no. I said by using iso type magnet and extracting, it's easy to extract. I think it's most easy to extract rare gas, for example, argon, neon, that sort of --

MEIGS: It's pretty hard to make those negative.

HATORI: Negative, oh! Negative, I'm sorry.

MEIGS: Yeah, that's the real problem. We have to have something that has a pretty good charge exchange efficiency, so --.

ROBERTS: You do that to get the radioactive isotope.

MEIGS: Right. You're right, we have them.

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"THE TUNL LOW-ENERGY BEAM FACILITY" - CARL BRUNE

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FERGUSON: Did you think about using a gas stripper instead of foils in the mini tandem?

BRUNE: I believe the reason we didn't choose to use a gas stripper would be problems with depolarizing the beam if we were doing a polarized beam, because I think you're talking about some sort of a gas cell which is differentially pumped on the end or something, so you would have the item neutral for a significance fraction of the time when they were in the stripper cell, and then you don't have a strong magnetic field monitor in that case then it would tend to depolarize, so the carbon foil we think is more likely to preserve the polarization?

HARPER: With these extremely low energies and relatively high beam currents, what's the approximate foil lifetime in this mini tandem?

BRUNE: It's highly variable but I'd say twelve (12) hours.

HARPER: And it's relatively easy to change the foils because it's in the air?

BRUNE: We load in about twelve (12) at a time, and you just turn the voltage down, and there is this carousel method which has a rotary D through which you just rotate by hand until it's in position. And if you need to change more than twelve (12) then you have to open up the vacuum which is more involved.

BERNERS: How much conductance do you have into those three turbo pumps on the chamber?

BRUNE: Are you talking about the -- the --

BERNERS: No, no the direct connection between the chamber and the three turbos that are mounted at voltage. I'm just wondering how the conductance to those pumps compares with the conductance through the accelerator tube to the ground?

BRUNE: That's a good question. It's a two-inch (2") diameter pipe.

BERNERS; Between each turbo pump?

BRUNE: Yes. And I would say that through the acceleration tubes, it's less than that.

BERNERS: Unh-hunh (yes). I just wondered.

BRUNE: I'm sorry I can't give you a better answer than that.

BERNERS: Yes, I guess you decided there was no way you could run your turbos on the ground and have a good enough vacuum?

BRUNE: Ahh --

BERNERS: I was just wondering, you might get a ten (10) to the minus six everywhere in the vacuum that's under stress -- with a different geometry, or maybe by increasing the diameter of that three foot long tube that goes between the three turbos and the one turbo?

BRUNE: Well, right. Well, we thought about that, and we got a two inch (") diameter for this tube here which should be big enough so that it's the pumping speed of this guy which is limiting the --

BERNERS: How long is that, three feet (3')?

BRUNE: Yes. The part that's on the high voltage is thirty inches (30").

BERNERS: Thirty inches (30"). Well, --

BRUNE: We actually used PVC pipe for the first go around. We think that was not the best choice. I think trying glass as an alternative which is what -- the acceleration --

NORTON: The beam current that you typically use the foil for twelve-hour lifetime?

BRUNE: Would be maybe ten (10) microamps, negative.

NORTON: And just a comment; what you really have there is an ungraded accelerating tube for your pump.

BRUNE: Unh-hunh (yes).

NORTON: Anything you could do to grade that would help to solve your problems.

BRUNE: We've actually tried that by running wires across from the acceleration tube which is graded and that seemed to not help our problem very much.

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"AN INTELLIGENT WINDOWS INTERFACE FOR THE KN 4000 VAN DEGRAAFF ACCELERATOR" - ALAN MCILWAIN

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MCKAY: What were the changes required, simply because the K3000 McMaster is even older than most of us here, and its parameters would not be the same as the modern machines. We see a huge difference between a modern K3 and a modern K4?

MCILWAIN: Right. Right. I think the biggest changes were the way they run their accelerator. Peter was able to hold the voltage stable enough on the 3000 just by tweaking the belt charge and the corona points whereas on our system which is running at the top of this voltage range nearly all the time, we need to stabilize it from running all the time. So, that's where the largest change is going to be. But the voltage program is similar but the operating logic is different. Again, they run it most of the time at one MeV, and we run, as I say, right at the top of our voltage range.

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"A MULTICHANNEL SPIN-ECHO NMR MAGNETOMETER" - CARL DICKEY

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BERNERS: What do you know about the parts and maintenance and repair situation, for instance, from Russia?

DICKEY: Well, I can only tell you about my experience, and that is, that they've been extremely good about providing spares up front and then turning things around if there is a problem.

BERNERS: Unh-hunh (yes).

DICKEY: My impression is that they're extremely concerned about establishing a reliable available track record in the United States. They really want to sell instruments here. And the nice thing is that with E-Mail if you have a problem you can get a hold of them immediately and they can respond to it. I think that if they were to sell quite a few of these systems they would probably establish someone, perhaps Duke, or someone else, with spare modules so that they can be had readily, but we've seen excellent reliability and they responded very quickly to our needs.

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"OPERATING THE KSU LINAC IN DECELERATING MODE" - TOM GRAY

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HARPER: You had mentioned, I think, that you believed the loss of transmission going along these low beta resonators is from the blowup of the beam --

GRAY: Right.

HARPER: -- from these horizonal yield components. Did you investigate your off phase acceleration any at all?

GRAY: No.

HARPER: You said you backed up fifteen (15) degrees, did you try going forward?

GRAY: No, we haven't tried that. That's something else we can do. We have a phase program that they use at Florida State. And, of course, we've been talking to people at Argonne. We get mixed messages; one of them say turn it this way, one of them says turn it that way. Also, we used a peak minus fifteen (15) degrees on all resonators.

HARPER: Yeah, but --

GRAY: We do that same thing accelerating, too.

HARPER: Yeah, that's what we do is peak minus twenty (20).

GRAY: Yeah, yeah. We haven't played games with the phase very much. You know what I'm talking about when I say a large parameter space.

HARPER: Unh-hunh (yes).

GRAY: So, there are a lot of things yet that we haven't optimized. It's kind of hard, though. It's kind of like trying to carry B.B.s in a fish net, you've got a lot of things to take care of.

JOSHI: What is the width _____________ of the linac.

GRAY: Our pre-bunched beam is typically two nanoseconds. And then after we go through the time buncher it's typically two hundred picoseconds.

JOSHI: What type of buncher are you using?

GRAY: We're using the Argonne, it's just a single gap buncher.

JOSHI: Argonne?

GRAY: It's got four different wave forms that gives you basic --

JOSHI: Argonne.

GRAY: Right. It's a standard Argonne design buncher.

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GENERAL DISCUSSION

HARPER: I wanted to make an announcement. For past twenty-seven (27) years Bill Weitkamp has been our technical director and he retired this year on August 11th. We'll miss him a great deal. He has a tremendous amount of technical expertise which we no longer have available in this lab other than by telephone, and that is if he's in town. And I think he intends not to be in town a great deal of the time. In some of his travels I'm sure that he intends to see some of you. He wanted me to say specifically that he will miss a great deal this particular forum where he gets to, or used to get together with a lot of people with the same interests as his for these long-term discussions.

GRIFFIN: Chris, any ideas for this general discussion?

WESTERFELDT: Well, I thought since we were short on time this morning that if any of the morning talks we had to cut short, if there were any follow-up questions over lunch that you got to think about.

CARTER: I'd like to maybe bring up a little something. You hate to wash out dirty linens, but I'm going to do it right here. We had some trouble with our high pressure gas compressor, Ingersoll-Rand gas compressor that we used to take gas in and out of the tandem. We had alumina balls in the filter that is on the output of the gas compressor. The gas compressor operating typically as high as sixteen (16), seventeen hundred (1700) psi for storage pressure when we dumped the tank. We recently changed out that alumina and it was loose particles in there, and so the gas in the pulsating gas from the compresssor beat the balls together and that dust into the valves and gave some problem with leakage through the valves. We are wondering if any of you had that type of problem in your gas compressor, and if you did have some problem with this filter system, what did you do to correct it? We've had one or two responses on E-Mail. One of them is quite unique, and we haven't tried that yet. I won't go into that right now. Anybody got some ideas on that or have had this problem, filter problem?

WESTERFELDT: This is a photograph of the filter, internally that's the basket that held the aluminum oxide pellets. You see the dust all over it. When it's opened up you can see how much of the material had been lost.

MUELLER: We have a filter on the outlet of our compressor, which is alumina filled. The only problem that we have had, once in the past, is that the hand valve

used to drain gas and oil out of the filter after each use wouldn't shut off anymore. We took it apart and found alumina in the valve. We replaced the alumina in the filter and cleaned the valve.

HILTBRAND: We did find a substantial amount of oil in the alumina, and I have not seen the problem that you're describing.

CARTER: We have what I think is a bit too much but not excessive. Oil comes through the machine. Originally, we had to service the Ingersoll-Rand compressor, and have it overhauled. And at that time which was about a year ago we found that the medium had just been caked solid, and that actually the oil and some of this powder had been promulgated all the way to the release valve at the top of your storage top. And so we know it moves quite a bit. This new powder and mixture of oil that got in our present problem had got underneath the seats on three valves on the manifold and we were unable to actually secure the gas flow solid and it was lifted in a three hundred (300) pound lift by bleeding through the storage valve, the high pressure gas control valve, and its shutoff valve. All that stuff just built up on the seats.

LAMM: ________ of our normal compressor and it does a very good job of trying to squeeze out of this thing. We changed the filter three times in pumping out our tandem. But the reason I bring it up is because we do have the alumina beads where we pass the gas back into the tank. We pass the driers, and I just had recently changed those beads after what, Ed, twenty-five (25) years.

BERNERS: About.

LAMM: So, the _______ is doing the job of trapping all out of gaps, if white beads are a good indication of gas. And I don't know if that's a suggestion to change the type of filter, but we certainly seem to have good performance in getting the oil out of our gas in coalescent filter.

CARTER: We're intending to get away from the alumina and go to a semi-coalescent-type filter probably using, I think, it was Tom recommended some filter material, I think. Okay. Thank you.

GRIFFIN: Any other topics?

GRAY: Yes. I'm going to hang out some dirty laundry, also. Over the last several years we've developed problems with our tandem. It's a model EN tandem and it's a random type problem. First of all, if you're going to break, break. The problem is as follows we're going to buy a terminal voltage, we're running along we might run a day or two, a week or month and everything looks fine, and beam is stable, the machine is running beautifully, and all of a sudden, bang!, the beam goes away. Your outlook on that is important. The beam is translated two centimeters (2cm) vertical. Moving two centimeters (2 cm), ________ vertical, we got Dowlish titanium _______________ spiral inclined field tubes. We thought well, we've got some kind of discharge going on, hollow discharge, tube discharge, something that's engaging part of that tube, the part that supposed to steer the beam back out ____________. Last May we went into the machine and took all the old resistors out and we put in the EBG which is a shield resistor using the Oak Ridge design, put the machine all back together and it's running beautifully until Tuesday afternoon. I went to the lab Wednesday morning to pick up a few drafts and the lab director caught me in the hall as I was scurrying to the copy machine, and he looked at me with a scowl on his face, and he said he did it again. And on Tuesday afternoon the beam was running along beautifully and all of a sudden, it flipped up two centimeters (2 cm) the first time ________. We thought we were going to be good boys and fix the problem. I don't think we fixed the problem, I know we didn't fix the problem. We're not quite sure what the problem is. It could be that we've got a bad resistor to get this thing placed for the same reason. It could be not a bad resistor at all. It could be some kind of a problem, short problem, dust bridge and that kind of deal. When we go in and look we don't find any indication of that kind of stuff, and we're kind of at a loss right now. If anybody else had an inclined field tube to observe any such random moving of the beam, and the way we cure it -- excuse me a second, John, is we turn the terminal voltage down and turn it right back up again and it's gone. And it might be gone for a month, it doesn't come back that day. It might be gone for five minutes, we never done it, it's one of those kind of things where you say, well, I wish you would break so I can fix you. But that's the kind of problem we've had. John?

McKAY: We saw something similar to that in the MP recently. It was running at high voltage. The beam went vertically, although it was erratic, it wasn't smooth, wasn't a simple transition. And when we went inside the only thing I could find in the first sections of inclined field where you suspect the problem was, were some dirty resistors to serve dust on the other side. But almost has to be in that first section because for one to move that much you really can't have a very strong beam. So, I think it's something in the low energy, and we just cleaned a couple of resistors off.

GRAY: I wouldn't think we could get through our exchange canal if we deflected to produce that much.

McKAY: Well, it's a small deflection found in the machine.

GRAY: Well, that's true.

McKAY: We just about lost the beam, but it's something in that low energy section, and if it is a dust bridge, as you're suggesting, when you turn it down that dust bridge might collapse.

GRAY: Right.

McKAY: So it might be simply be a buildup of dirt somewhere.

GRAY: I've been looking at the high-energy side of the machine. My problem of thinking was, well, it's got to be on the high-energy side because once you go through the stripping canal, I mean, if you deflect a bunch going in you have it right to the stripping canal. You've got a three-eighths inch (3/8") hole.

McKAY: I don't think losing one plane in high-energy is likely to do it, though it might in that first tube section, but I think I'd be more inclined to look for it in the low energy tube.

GRAY: If you look at the machine everything looks okay. Power currents look fine. All the voltage signals look fine. All the visual stuff all looks good. You can't find anything wrong.

McKAY: That's very similar, we were up just in the inclined yield section, so that's up about twenty (20) planes of half value resistors where its straight in our tube, and just in the first inclined section there were some little dirty resistors. I haven't fixed it and had it go for a year yet so I may not have fixed it.

GRAY: No, we don't have any gridded lenses or anything going in. If there were radiation, if it was tubes breaking down, we had a bad section of the tube that was going sour on us, there is only about forty-five to fifty (45-50) or so kilovolts all across a section at maximum voltage, and the radiation you see from that might kill it off in the tube, it's so efficient at killing off discharges, you'd never see it anywhere else. That radiation is so soft you can't see radiation outside the tank wall. My thought was we might need to go inside the tank and put a radiation detector inside the tank.

McKAY: Well, I figured if it was discharged along the resistors outside shorting out the inclined field. So, it's just a little bit of arching in the SF6.

GRAY: Okay. We've tried increasing tank pressure, it doesn't change anything. We tried changing the characteristics in the insulating gas going from like sixty-two (62) up to seventy -- seventy-five (75) pounds.

HARPER: We had a problem that was similar to this, I think, that might have been reported on a couple of years ago.

GRAY: Belt slap?

HARPER: Yeah, it was a belt slap. But the only difference is that there was a change in the high energy column current because you start to lose some charge to the column. Everything else is similar. It would oscillate occasionally, sometimes it would be two state. As soon as you would turn the belt charge down the belt would snap back into place.

GRAY: As far as we can tell this is not oscillation. This is a bang! I mean, it's up there, it's not going to come back.

KRAUSE: The machine is just as stable as it was before. The beam just goes away.

HARPER: Sounds unstable somehow.

KRAUSE: Well, let's say the GVM, corona, everything's just fine.

WESTERFELDT: When you arc the machine and you megger it, do you megger at five kilovolts or anything like that, or is it low voltage megger?

GRAY: Five kilovolts.

LAMM: Do you have any sort of shorting mechanisms where you can go plane by plane and try to find something that causes this same -- an inch or so displacement of the beam, anything -- can you use something like that possibly, or just to go down each plane one at a time and try to find some similar?

BERNERS: We've gone to that extent by dragging a shorting bulb along the column, we haven't gone to that extent.

LAMM: Okay. Second question, Tom, obviously with that big a shift you can't get that beam optimally where it needs to go, but can you get it to a cup where you can measure the intensity? When this happens is the intensity pretty much still there?

GRAY: Well, no, we don't have a cup before the analyzing magnet, any of the magnets, we'd have to put a cup in.

LAMM: Okay. Same question, is there anything else going on in the stripper mechanism? In other words, when you dial this terminal voltage back down and back up or are you likely not to change foils?

GRAY: No, no. This was running under gas conditions. It happens under both gas and foil stripping conditions. It doesn't seem to know where the stripper is. Doesn't seem to know where the beam is. It happens to him when he's running the carbon beam, and it happens to us when we run the chlorine beam, it happens to Pat and his group when we're running or carbon beam. It's not being selective.

GRIFFIN: The displacement is always about an inch or so you say?

GRAY: Yes, this order of centimeter -- point one two (.12) centimeters.

LAMM: Is it always up?

GRAY: Not always. About ninety percent (90%) of the time it's up. I have seen on rare occasions I've seen almost kind of like let's see, twelve o'clock (12:00), two o'clock (2:00), maybe two or three times out of thirty (30).

JOSHI: Principal we have a beam for point ______ in field but I can't see here for point eight (.8), point nine (.9), machines sparking, __________________ slow, what I want to know is this a problem with ___________ or is this a problem with the machine?

JONES: What kind of sparks are they?

JOSHI: Tank sparks.

JONES: Yes.

JOSHI: And also we simply beam last year we had ___________going. Last year we had problem of tank sparking of the machine, we opened the tank and we found the problem breaking down of the rubber couplers in the rotating shafts, and also _________going back so those things were _________ back and all things work well. But it appeared the high definition created problem for ___________ towards, also. And because of those things it complicated, the problem of the rubber couplers of the relating problem and we tended to work up little T to the high ___________ section. And since then it is working fine. We have not had any problem. I want to know what is the life of the rubber couplers which are working into this rotating shaft, and other thing is any precautions we can take for this position, or part of the ______________ problem?

GRIFFIN: Anybody have a comment they'd like to make on this question? Greg?

NORTON: No I am sorry I don’t have much to add. The only thing I can say is that we do not sell very many rubber couplers. This means that they tend to last a long time in most of the large machines.

JOSHI: Since we have a lot, for instance, column groups also, and we've had _____________ so as we already see I just want to know what potential we can reach with compressed geometry? Just an idea.

NORTON: I am sorry I can’t be more quantitative. Maybe we get an order once or twice a year for a total of about a dozen machines. Part of the problem concerning longevity has to do with how the machine is run. Your machine may be well ahead of other machines in terms of hours and the number of discharges. We know of no specific time for recommended replacement under the conditions found in electrostatic accelerators.

GRIFFIN: Excuse me, you mentioned the compressed geometry?

JOSHI: Potential of the machine with compressed geometry, and we have knowledge of waiting, knowledge for columns and tubes both, so what I -- my work I can achieve now, is it some of you from sixteen (16) MeV, or is it the same?

NORTON: With the column diameter that you have with the compressed geometry tube, the only similar machine is the ANU 14UD. Any trend with only two machines would be hard to quantify. Although they have a compressed geometry tube, they removed part of one unit to install a post terminal stripper so they really have a 13-2/3 MV column. They have run experiments at 16 MV.

Your machine with 15 units is running at a lower gradient than the ANU 14UD. The ANU folks claim they are now tank limited because they are limited to 125 psi SF6 and they have tank sparks at 16MV.

The maximum gradient that can be expected with the machine has a lot to do with how you condition the machine. There is no magic procedure. I think that the Oak Ridge group is probably the most conservative. The method to achieve the highest terminal potential for a large accelerator was probably better addressed by Charles Jones or Martha.

MEIGS: No!

NORTON: But there are a lot of variables, but the conditioning, method, changes, and so on are very important for machines with that amount of storage. You get good sparks, you get bad sparks.

JOSHI: ____________ using by the column by the _______ that we, so that look like we're going to high side and then to low side.

NORTON: Well --?

PARPART: I would say the voltage has retainable resistors that you want to confuse with your corona points. Again, it's going to be limited by the columns to the tanks. I remember when I was there we couldn't _____________ side at sixteen point three (16.3) MV. So you could run over sixteen (16), given that the tank and the machine is in a comparable position of what it says. Actually it would be easier to reach that potential now because the tube is, what, four or five years older I believe. So, its aged a bit. So the machine is clean and you _________ condition. And with Australia's experience, it should be quite feasible to get over sixteen (16). It may degrade more quickly if you're going to try to get more degrading sparks at that potential because you're pushing the machine. The one thing would be, again, as Greg mentioned, more gas. You do have to watch how much gas, if you get too high ____SS you're going to weaken the protection of your spark gaps on the column of the tube. But I believe if you go up to about a hundred five (105) psi on the gauge you're going to be okay as far as the spark gap should hold.

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"FORTY-FIVE YEARS OF NUCLEAR PHYSICS AT DUKE/TUNL" - PROF. E. G. BILPUCH

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GRIFFIN: How come you had the frogs jumping around in the corner instead of the Wolfpack guy, and the ram, and the --

BILPUCH: Well, I just tried to change that a little. I don't know why. I mean, I like frogs. And our graphs woman was great with frogs, and -- so that's okay. I think I do have the UNC and Duke and North Carolina State jerseys on. This one, I -- yeah, that's good enough. It's got a couple of jerseys on it. I like frogs. My wife is a frog collector, so that tells you why.

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"STATUS OF THE ISL AT THE HAHN MEITNER INSTITUTE" - PER ARNT

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ARNDT: Yeah, okay. It's late already. I know most of you are tired, myself, also, so I tried to make it as short as possible. The title of my talk is Status of ISL observed at the Ion Beam Laboratory, Berlin. So that's a overview of the research program.

(Next slide.)

I am not going through all of those, but direct ones I'm talking about especially the ion source development of the RFQ project, the eye tumor therapy, and that's canceled, how about that, nuclear physics.

(Another slide.)

Here is a new overview of our lab. Here, so that shows you the __________ of the situation in the future. We have now the CN, 6 MV injector, we have the cyclotron, and we have the experimental area. Hopefully, in one year we'll have finished the two hundred (200) kilovolt injector for the new project, and we will have eye tumor therapy. For those projects I'll give you a short information.

(Next slide.)

Here is another overview. You can see a little bit more of the beam line, and you see also the relative complicated beam line especially for the eye tumor therapy and the RFQ. And you see also the size of the scale for the centimeters, so let me begin with a new project, the RFQ project, and that's the injector assembly. That's the injector the injector of this, of the old two hundred (200) kilovolt NEC tandem injector. We used this one to install the ECR source. The ECR source will be the full permanent magnet ECR source following, forty point five (40.5) gigahertz, operating between ten and twenty (20) kilovolts, and you see the emittance, we think the ion source will have four hundred millirad. The charge to mass is one eighth or one sixth. That depends on the ion you are using. The source itself will have in weight about one hundred thirty kilograms (130 kg). And we bought it from GANIL, and we hope to get this ion source November '95, so next month. And just the -- okay, that's quadrupole and dipole as usual. And then the beam is injected into the RFQs. We have two RFQs, one is beam RFQ, I don't know if everyone knows that, radio frequency quadrupole. It's a very interesting accelerator type because it's consistent something complicated mechanical inserts. And you need outside of those ones only in r.f. power supply, nothing else, nothing is moving, nothing needs very complicated quiz system or anything else, very simple. And you see our frequency range, and what's interesting, we have an energy gain of six, and that's in -- the whole length of both RFQs about two meters, you can have energy gain of six. Okay. That, I show you other overhead about the RFQ, how it looks inside, how to calculate such a RFQ is known already. Here is one like with making that as a group that's not a complicated thing anymore. By complicated, very complicated is the manufacturing of those rods here, they're one meter long and the accuracy of manufacturing these complicated rods must be better than point zero one millimeter (.01 mm), so that's very complicated over one meter (1 m) to do that. But you have do it in that way because those rods are compressing the beam and X-ray beam within the RF. That is the basic idea of an RFQ compressing and accelerating, so the factory who is doing that for us now, manufacturing these ones, they have a little bit difficulty, we thought they have a difficulty. We hope to get these RFQs May/June '96. There are also difficulties with the r.f. powers supply from Varian, and they also deliver these house supplies. We need two for the two RFQs, also May next year. So. for this project, we hope to get everything together July or August next year, and so we'll see what happens then when the first beam is injected. But if -- we were sure that system builder, I don't know of the difficulty, but if that system works, it works really -- every time, it's nothing changeable anymore. But until it works, that might be not the one-year work. So, the other topic is the ECR sources. As you know, I gave a talk about the BECRIS source last year. The BECRIS source is working now for two years very satisfactory. And for those one who don't know what ECR mean I have the principal over here, it shows you what happens when you inject atoms in such a system, system of axial regular magnetic field. The axial magnetic field is a special one, because of electrons who are moving within a static magnetic field at its own frequency. And if you have the right frequency injecting to the electrons moving at a special magnetic decelerated. That is the principle of ECR source. It is well-known how to calculate such source. We calculate our source. We have also calculated now the new source for the RFQ project, and we will calculate, we hope so, if I get the money for that, a new ten (10) gigahertz ECR source permanent magnet like the GANIL people are making, but we will do it another way. So, I mean ECR sources are really the best responder of the beam source and so on, because the last two years we have no problem anywhere. But in a moment, with our _______ sign source we had some problems. We don't know why the higher charge state ions analyzed after here is only fifty percent (50%) than it was before at the beginning. We don't know where the ions are lost. It might be that it's in recombination of anything else. We don't know where the ions are lost. We have measured the magnetic field and we don't find inside the plasma area any change of the magnetic field. Outside we find that the magnetic field is changed outside the source, often quicker than before, so because you have -- if you have a magnetic system you have outside the source here and here (indicating), a magnetic field restoring the ion beam, and we think that it might be that this field will have changed as we measure it, and that will change also the compressing of the beam outside the plasma. So, we don't know really why it happens. Now, that is an overview of how it looks like in our terminal there at the ion source, the plasma side, very insignificant, five gigahertz, two hundred (200) watt made fully ______ and the whole power consumption of these power supplies, nine hundred (900) watts, or two hundred (200), five gigahertz.

(Next slide.)

That's better view. That's _________ and that's the gamma source we have six gases inside the terminal. So, because of the problem to be, we began to calculate the beam transmission out of the source and that looks to be very complicated. We have now got two weeks before as the people told how the best program to calculate has complicated the system, that is called override. I don't know if someone knows that. It's very complicated system -- program. And we just began to calculate these -- with this -- with override it's possible to -- to calculate electrostatic and magnetic fields together. And that is very complicated, for those ions will begin to operate with these apparatus, so we just began and that's our ______ type. Yeah, and the next topic is the energy spread of the CN injector. Years before I talked about the _________ of our CN. Someone of you have heard about that. I gave a talk here at SNEAP. It got this on the regulation ring between spinning tank, tank wall, we use the relays therefore because it in summary, the capacitance -- caoacutabce between the ring and the spinning is everytime the same. So spinning is moving little bit, but the summary is the same. And so there is odds of that regulation system is -- here we have the normal two -- two point five (2.5) kilowatt ripple, and then afterwards we have two hundred forty (240) volt ripple. Works very good but as usual, people tells can you do it a little bit more better especially because as we see now we make ions from one MeV up to fifty (50) MeV, so they are a great run to that CN injector. And if you have low energy excrement, the energy spread has to be as small as possible, so the two hundred (200) -- two hundred and fifty (250) or three hundred (300) e-volt was not good enough for every exponent, so what have we done? We change the regulation slip after this year, and it looks like the width here, it is fully closed with a negative voltage between hundred and eight hundred (800) volts. We have a primary slit with positive voltage between ten (10) to fifty (50) volts, and you see the difference between the regulation slit and the traversing slit is one point five millimeters (1.5mm). It looks simple, sure, but I can tell you that with this system now, we have only fifty (50) e-volts energy spread and it works very well. And what you have done is our beam is much more better than we thought. We can reduce the width of that regulation slit with our system which was normally three millimeter (3 mm) down to point two four millimeters (.24 mm). And we lost the beam, about ten percent (10%) on. So, the emittance of the ECR of the vector source is much more smaller. And we use regularly for the regulation the right beam and not some electrons or coming out around the beam. So, I mean that was a good step. The last point is the eye tumor therapy, the contracts between the clinic and our institute is unwritten. And so the works and the buildings are begin to build up, and we are using a product mean, seven- -- seven-two MeV proton beam. Why are we using a proton beam? You can also say why don't you take the argon or something else. I have an overview.

(Projecting another slide.)

The normal way, if you have a tumor which you can't operate anymore, you taking gamma, you turn on your -- the eye of the patient put a gamma ray plate, it's behind the eye, and then -- yeah, you doctors hope that the tumor will be killed. It's not a good way for the patient, because normally they lose their eyes. In Germany we think we will have about two hundred (200) patients. And for those ones we will have these protons, the tumor therapy. Why are we using these protons? To see how different it is when proton gamma ray- -- electron rays are penetrating material. You see that is a normal for the gamma rays, electron -- electron one, and that is the most important one is for the proton. Why is it so? It's just proton beam comes into, for example, this eye. The electrodes in the material has its own velocity, and the good thing is that if a proton comes in, it goes through the material and the eye, for example, the eyes, not -- it goes through -- it has no contact to the -- to the material, protons and electrons. It goes through but it lost already a little bit of energy. Well, yeah, but when it comes into the areas of the electron velocity of the materials, and that segment we lost most -- ninety percent (90%) of the energy at that point. And that is the reason why we are using the proton beam much more better is to take helium, but for helium you need already over two hundred (200) MeV helium. We can't do that because for helium it is -- that means about one millimeter (1 mm) helium. One or two millimeters, so for helium you have an accuracy of about down to point five millimeters (.5 mm). That would be much more better for the therapy. We are using the proton beam.

(Another slide.)

And here, this is how it looks like in our lab, hopefully in one year. Here somewhere we have a window where the beam is coming out of the cyclotron, it is here and here already. We have a colon for it and it is in here. We have a range modulator because you must modulate for every patient a special energy because you must know -- in front where the tumor is -- you know -- how great the distance is, how long the -- how many eye of the tumor, I don't know the right way, you have, so you know how much energy the proton beam has to lose to be on the right place to hit the tumor. And so we may be in front, every patient gets his own MeV range modulator, is only for her -- for him, and then we have an aperature for every patient. And the patient has a mask, shields his eyes, and he takes some light. And the problem is, that the patient's eyes have -- having to move within the shot. The shot, that means about twenty (20) seconds, thirty (30) seconds. That's all, two times within two days. That's all. And the good thing of this therapy is that apparently that after five years those patients will have no problem anymore with their eyes, with the tumor, or anything else. It is about eighty-five (85) to ninety-five percent (95%) over-living the therapy. Normally those patients lose their eyes and for -- they are better still in the -- in your bodies, they sometimes dies already. So, it is really a very good way to use an accelerator for the beam. Okay. So, we hope in one year we make the first need for patients. Okay. I'm on time except -- Thank you.

McKAY: Do you have a table of what the beam currents were out of the metrix source? What fifty percent (50%) lost problem?

ARNDT: Oh, for example, after the CN, r.f. A plus, we could consult gas mixing, so no, I don't speak today about data. You know -- the gas mixing of ECR so without any gas, most possible to make two, three hundred (200-300) nanoamps energized beam. But in this moment we get only half of them. We really don't know why. The power we need is not more than fifty (50) watts, sixty (60) watts. For simple beams like nitrogen, one, two, three plus, or ducherium or helium, or so, we need ten (10) watts, fifteen (15) watts, we have hundreds of micrograms. So that's as many, but the highest stage that we are real problem at this time. My opinion it is a combination. But it's really -- we're surprised, we open the spectrum after two years, we want to clean, and we thought we find a lot of things. We don't -- really find only a little bit of carbon inside the source. That's simple because we use carbon monoxide to make carbonate, so that's all.

McILWAIN: What was the maximum range, about seventy-two (72) MeV in the eye tissue? Did it penetrate _________?

ARNDT: We use only seventy-two (72) MeV.

MCILWAIN: Yeah. What was the range in the eye? How far did it penetrate without modulating?

ARNDT: Yeah, look to your eye.

McILWAIN: The thickenss of your eye?

ARNDT: Yes, that's what really show you it's about one centimeters (1 cm), that depends where the tumor is sitting.

MCILWAIN: I was wondering why you chose that energy?

ARNDT: Yes, the modulator. Because it goes really through your eyes. Doesn't do anything to your eyes, it goes through.

GRAY: What is your ambient vacuum with the ECR source, what's your ambient vacuum for the whole place?

BERNERS: Yeah, we begin with a problem with the vacuum, right, especially in our case, how we infiltrate the air up into the source. It's different from the normal air source. Inside the source we have ten (10) to minus seven, and when the source is running we have ten (10) to minus six.

GRAY: So, your recombination is going to be high?

ARNDT: Yes, yes.

GRAY: Especially the higher the charge that you have the worse it's going to be.

ARNDT: You know -- sitting there up in the terminal we are glad to have the tumor glob on the inside but we have no space to put a second one, or a third one, or I can get a __________ where an ECR source one rule is to have a very good vacuum, especially for the high change. You're right, but we can't change that. But in this case it is the same tumor glob, the same good vacuum, or bad vacuum.