MUCOOL Meeting Minutes 3rd February, 2000 Scribe: Steve Geer 1. More on scattering ... Alvin Alvin made the case for consideration of a very precise scattering (and straggling) measurement with a thin and a think liquid hydrogen absorber ... with perhaps the goal of a 0.1% measurement of the width of the scattering distribution, etc. Before we understand the need for this measurement we need some feedback from the simulation studies to tell us whether small uncertainties in the scattering models have a significant impact on cooling performance ... if they do the measurement needs to get made. 2. Experiment design updates (a) Steve Kahn Steve has looked into the question raised a couple of weeks ago about what would be needed to measure the track within the solenoid channel for the simple experimental setup we have recently been considering. Steve says we need 3/8 of a helix to reliably measure the track parameters which means a tracker length of about 1 m. If the solenoid was 2T (1.25 T) its diameter would need to be about 50 cm (80 cm). (b) Don Summers Don has investigated the angular resolution that could be expected with the fairly simple tracking system he has been considering for the beam experiment. He notes that a 50 micron mylar window = 1/5000 rl, 1 m helium = 1/500 rl, and the contribution from a typical drift chamber gas might also be about 1/5000 rl ... all together we might get away with a total of 0.01 rl -> 10 mr scattering angle. Don thinks it might be possible to squeeze this down to 3 mr. 3. Cooling channel update (a) Mike Zismann DFOFO design has been put on the shelf for the time being due to very high fields (20T ?) within the closely spaces coils. Dan Kaplan pointed out that having short fat coils more widely spaced rather than thin long coils closely spaced might help ... and is going to study this. Jim Norem suggested considering iron washers to lower the flux in the coils. (b) Paul LeBrun Paul listed on going simulation activities at FNAL. Pauls summary: " The Optic and Cooling group at Fermi is actively pursuing multiple studies of various designs of cooling channels. All of them are based on the use of relatively high field solenoids, and 175 or 200 MHz r.f. cavities. Absorbers are either LH2 or LiH. They differ by their architectures, that is, the shape of the beta function, the distance separating each beta min and/or each absorbers, the length and type of matching section between cooling sections and their longitudinal and transverse acceptance. Rather than studying in great detail one channel, as we have done for the 15T. Alt. solenoid, many of us went to studying "architectures". - DFOFO, or "double FoFo, where a second beta min is inserted in the middle of the LINAC to defeat multiple scattering in the middle window of the r.f., and provide some elbow room to insert the LINAC. The design comes from LBL, we want to verify the performance of this option. Dave N. and Dave Kaplan are working on ICOOL and DPGeant, respectively. Issues are: (i) maximum magnetic field on the coils (ii) input beam characteristics, particularly longitudinally (iii) performance measurement: yield within 1500 mm. mmRad versus distance. However, Dan is still struggling to reproduce the performance in DPGeant, the loss are still very high. Eun-San will send the input beam file to ease the comparison task. - Continuous Solenoid, followed with adhoc field flip to cancel canonical angular momentum, followed by a second section with constant field, proposed by Valery B. and Yaruslov D., worked by Valery. Once the matching section, with a well behaved beta function, is designed, valery noted that the longitudinal matching becomes very hard: the Palmer correlation gets strongly disrupted, because, when the longitudinal field goes to zero, so does the transverse momentum, causing a sudden displacement in the bunch. in Delta Z. - Jocelyn is investigating a similar configuration, where the field is not constant in the coolers: we can reach a smaller beta min at the absorber by increasing the field there a bit, which we can, since absorber has a smaller radius than the r.f. cavity. . She is currently woking on the optimizing the matching section, (transverse, studying the beta function). - Adiabatic SoSo. Paul L. The idea is to take a SoSo configuration, which cools fine over roughly 60 m and cools by more than a factor two, and slowly ramp up the field and decrease the beta min, so that the cooling rate is sustained though the entire channel. An almost constant cooling rate has indeed been achieve over a short distance (25 m.) , we now have to keep building on this .. This optimization is a slow process. - Sensitivity to multiple scattering, detailed models of scattering . Alvin T., and Paul L. , (earlier work.. ) This work has been presented before. - Optics in Solenoid. Based on the work of Greg Penn, Dave C. and Jim N. are indepedently trying to come up with a deeper understanding of the optics in solenoid, so that analytic solutions can guide us in the design process. Although there is great pressure from the Neutrino factory people to focus our effort on a particular design, a few of use are still working on improving or changing the basic design (e.g., lattices) of these channels. " 4. List of cooling experiment tests Steve Geer A list of possible reasons why a cooling channel might not work was presented together with the simplest experiment/measurements that would address these possible problems. The list, including some additions from the discussion, is: Possible Problem Experimental Test 1. Inadequate scattering or Scattering/straggling experiment with a straggling model simple geometry and no field, and possibly also in a solenoidal field. Comment: we need to understand whether the cooling channel performance is sensitive to the remaining scattering/straggling uncertainties before we can know whether this is needed. 2. Absorber density gradients Absorber beam test ... use proton or electron beam ? 3. RF gradient not achieved RF bench test in solenoid and radiation in radiation & magnetic environment field environment 4. Magnetic field quality Measure prototype on bench not achieved 5. One or more components Prototype & test each component in not radiation hard radiation environment 6. Inadequate instrumentation Needs a paper study ... then we can discuss to debug and operate details and possible instrumentation tests channel in hot electron or proton beams. 7. Accumulation of small Beam test a long channel ... length limited effects by affordability. Comment: we need some feedback from simulation studies to guide us in choosing a sensible length that enables us to see plausible effects. 8. Space charge or other Catch 22 ... need the full muon source. collective effects Comment: This means convincing paper studies are important.