Minutes of the MUCOOL Friday Meeting 14th Jan, 2000 Scribe: Dan Kaplan LBL report: ---------- John Corlett reported from LBL on the progress of commissioning the test solenoid. Mike Green had reported that in "solenoid mode" the coils reached 90% of design current. Coil 1 was training and they postulated that it was due to presence of iron in the carriage of a nearby dewar. They will try again with the dewar farther away. In "gradient mode" the coils have reached 104% of design current - in fact they continued to work even after the LHe boiled away when they ran short! Now warming up and cooling down for 1st time, now at 120K, cooldown to resume shortly for continued tests next week. Derun Li reported on test of windows with a 100W halogen lamp. ---------------------------------------- Room temperature tests: Al window: center-to-edge temperature difference delta-T up to 93C failed to cause measurable deflection on dial indicator but at 80K the defection was 127 mils. 5-mil Be window (pre-stressed): no deflection up to delta-T of 27C, 1/2 mil deflection at 33C, 32 mils (or 800 microns) at 59C The deflection is needed to be <100 microns for the 805-MHz cavity. Tests at LN2 temp: dial indicator "froze" and stopped working, so they measured the frequency change of a 1/2-cavity instead. Al: large df/dt Be: negligible df up to dt = 176C sudden df at dt = 198C RF heating test up to 400 W (expect about 10% of this to be dissipatd in window) gave 20C dt in Al window, only 1C in Be window, but interpretation not clear since some power could have been dissipated in cavity joints. They will analyze further and write up. Absorber ass'y/testing plans (Cummings) ---------------------------- Mary-Anne reminded us of the 2 designs, convection-cooled and flow-cooled. Ed has drawn up both designs with dimensions L = 56 cm, r = 20 cm. Ed has proposed a tapered ellipsoidal Al-alloy window 50 microns thick in the center and 3 mm thick at the edges. We are not yet sure that this is thick enough to take 2 atm pressure differential - finite-element analysis in progress at IIT. Rick is adding to ICOOL the ability to simulate such shapes. Geant can also handle this but it has not yet been coded or run by anybody. Ed should put these drawings on the web. Near-term goals: 1. establish ~500W power-handling capability (Norbert asked whether this was for 1MW or 4MW proton beam - it is for 4MW, but also for short absorber, so may be an underestimate for a minicooling absorber) 2. optimize arrangement of temperature instrumentation 3. engineering/cost estimate/safety review 4. build and test 2 prototypes Crude schedule/budget: 1. establish safety review board (Jim Kilmer et al.) 2. destructive tests of windows - could do at IIT with H2O ~30k ~6 weeks (window delivery est. 4-6 weeks, windows ~7k each) 3. "Stand-alone" tests at FNAL ~6 months need: 4 thick windows to hold penetrations for ~30k heating wires, temp. sensors 2 absorber vessels ? 500W LH2 refrigerator ~500k 4. high-power beam test Norbert reiterated his request for neutrino factory cooling-channel power estimate - this could depend of course on the efficiency of the cooling, which is still being optimized. People were concerned about cost of refrigerator. $150k could be saved by finding a surplus compressor. Alvin suggested using big He dewars instead, but this may not allow a full test of all engineering issues. Maybe a surplus refrigerator can be found at some other DOE lab? Scattering theory (Alvin) ----------------- The Rutherford guys are considering doing a multiple-scattering experiment and wanted detailed predictions from Alvin. Alvin reviewed background he has presented before on Thomas-Fermi atom vs. actual hydrogen wave functions and Z(Z+1) factor which does not apply for hydrogen. He concludes that 10 cm of LH2 should give a taller and narrower distribution wiht a broader tail than Moliere, but the two distrib's cross at 10 mr for p ~ 100 MeV/c which means that it is a hard experiment depending on measuring the tail out at very low scattering probability. Jocelyn will run detailed Geant calculations and compare with Alvin's calculations, also investigate logarithmic corrections to the sqrt(L) thickness dependence. Megnets and beam files for MUCOOL (Kaplan) --------------------------------- Earlier in the week Dan distributed to interested parties a list of available magnets compiled by Peter Garbincius in 1996. He had also emailed hbook files of muons simulated in DPGeant traversing an LH2 absorber in a 1.25T solenoidal field, taking input distributions from one of Mokhov's production/capture MARS runs. He was asked to produce new files using an input muon distribution expected in the MUCOOL test beam. MUCOOL experiment design (Fernow, Kahn, Summers, Hanson) ------------------------ Rick and Steve have begun ICOOL simulations with an input 200 MeV/c "pencil" beam of 1500 mm.mr transverse emittance (such as produced by the D2 beamline). They simulated a 2m absorber of 20cm radius in a 1.25T field. After the absorber they find an emittance of 3000 mm.mr. They assume a BM109 to deflect the incoming beam. Downstream of the absorber they want a short magnet with a large aperture (in order to put MWPCs inside), but not too large an aperture (to provide a quick fall-off of the fringe field). They have tentatively selected from Garbincius's list the E683/SCM105 magnet, which is 60" long (including shield plates) and has an aperture between the pole pieces adjustable from 14" to 40". They assume 2 x-y measurements on either side of each magnet (plus one in the middle of the SCM105), with 300um-r.m.s. resolution, to determine momentum and direction on each side, and particle ID before the 1st momentum measurement and after the second. (Better resolution, say 150um, is easy with drift chambers.) The x-y measurements are separated by 1m with 1m gaps surrounding each magnet to let the fringe field die away. At 10 kg the outgoing 116-MeV/c muons have a bend radius of 37 cm. They have no matching between the solenoid and the spectrometer. In the vertical the SCM105 aperture can accomodate about 2.2 sigma of the outgoing beam, and about 4 sigma in the horizontal. They believe this arrangement can measure emittance to about 1%, neglecting scattering of the muons in the spectrometer. They will also consider the "Jolly Green Giant" magnet. Steve Geer proposed the following sequence of measurements: 1. no material (optics check) 2. material but solenoid off (check multiple scattering in LH2) 3. material and field on Dan suggested going beyond 1.25T solenoidal field (to explore suppression of scattering in a strong solenoidal field) as well as mounting the solenoid and absorber on a turntable and translator. Don discussed resolution considerations. He considered momenta from 100 to 300 MeV/c. In a 1T field these are deflected with radii from 0.33 to 1 m. A 1m length will deflect a 300 MeV/c particle through 60 degrees. Gluckstern, NIM 24 (1963) 381 explains how to optimize momentum measurement. A He-based MWPC gas such as 80:20 He:isobutane has an 807m radiation length, 6.5 times longer than that of the more usual Ar:CO2 mix. Helium between detectors is also important, with a 5300m radiation length, 18 times longer than that of air. He suggests chambers with 20um Au-plated-W sense wires and 55um Au-plated-Al field wires. (Au-plated kapton foils may also be an interesting possibility, as used e.g. in MEGA and NuSea.) Gail has begun an analysis of what measurements and resolutions are needed. She would like a field-off hbook file.