**** 8/13/99**** 1. Discussion of mucool note 39, Kirk T. McDonald Title: Emittance Diagnostic Channel for R & D on the Front End of a Muon Collider / Neutrino Factory The note compares parameters and discusses instrumentation issues for a targetry experiment and an initial stage cooling experiment. Calculations are based on (BNL?) analytic estimates developed for the emittance diagnostic channel for the final stage cooling experiment. -1.25 T in the cooling channel is chosen (for targetry concerns) to match upstream magnets. This number could vary. -Phase space parameters of the muon beam at the beginning of the cooling channel at a neutrino factory are listed in Table 1. Kirk's highlights: --momentum spread for 1.25 T is 10%, a larger value than in the later cooling channel. --normalized emittance is 9000pi mm-mr at this point. The initial value would be 15000pi mm-mr, but is "mini-cooled" by 3m of liquid Hydrogen in the phase rotation channel. --P(0) = 185 MeV/c --E(0) = 198 MeV -A comparison of targetry and cooling parameters for 1.25 T bent solenoid channels is listed in Table 2. Kirk's highlights: --0.1 rad momentum resolution is accurate enough for the targetry channel for weak field, weak bend if the tracking chamber is 50 cm long. --0.25 rad momentum resolution is fine for the cooling channel due to the emittance. (geometric emittance = 5100pi mm-mr.) The emittance numbers come from Bob Palmer's parameter list as of 8/3. --33 clusters/m is given at 1/100 atm methane, lower preassure for isobutane -instrumentation: --TPC length is unchanged from earlier studies, however the diameter has increased. Pad width is now 20 cm; laboratory studies need to be performed to verify that spatial resolution of 200E-6m can be achieved. --Will the tracking be acceptable with these TPC parameters? Steve Kahn is simulating them in DPGeant, with no junk hits, and gets (roughly) the projected parameters. 2. Low Frequency RF Designs, 8/12 Video-conference Update Al Moretti Participants were Cern + collaboration, transparencies will be available on the web by Monday, next meeting is 8/26, contact Kirk about agenda. Meeting as follows: --Kirk on target expt. at BNL: LBL will supply surplus RF amplifiers w/ 1.25 MW @ 70 MHz, peak surface B field of 15 MV/m. LBL amps will be used to power BNL cavity, positioned after the target chamber. --Al on low freq. RF designs (showed at mucool meeting last week): grill over aperature cavity design. 201.25 MHz cavity. This cavity design approaches a pillbox cavity (which has the best shunt impedance) with increase in the number of rods in the grill. Advantages of the grill design: -rods more rigid than thin plates -could use holes (btwn rods) for cooling gas, which may be necessary with 100 MW deposited on rods (temperature gradient of 100 C.) -Ratio of surface area to aperature size is 40% for an 8 rod plate; this is not a constant quantity throughout the cavity (Paul LeBrun) -Need to minimize wall thickness. 10 mils might be possible with construction grade Be, 97-98% pure. However, even 1% Cu would dominate multiple scattering (disastrous), although radiation length Cu/Be = 1.4 cm / 35 cm, so MS might not kill us. -Alvin suggested pie shaped rods to solve the expansion problem, difficulty is how to prevent electrical breakdown on sharp edges, where field is enhanced 3 - 4 x,(motivation for cylindrical rods.) 3. More Low Frequency RF Alvin Tollestrup ~ Discussion of paper by Ratzinger et. al. presented at last LINAC conference. Ratzinger was a no show for MUTAC. IF only he had come Al could have told him that his calculations are off 10 - 20 % because MAFIA didn't calculate the fields correctly. -Paper covers training behavior of Cern 3 tank drift tube linac @ 200 MHz. Pmax = 1.3 MW, acc. gradient 10 MeV/m. -they measure the power input then calculate fields with MAFIA, though it is unclear how or where they calculate the fields. -Scary result: dark current peaks at 150 mils of electron current, where all power is going into dark current. Radiation levels here are .5 mrem/hr*duty cycle @ .8 Hz. Danger to drift chambers. However, the more gaps in the cells, the lower energy x rays, and if you back off the power by 15% dark currents go way down. And, these guys do not llok at on-axis radiation levels, which is what we want. general information: ************************ * 1 severt = 100 rem * ************************ 4. Sensitivity Studies w/ 8 T SFOFO Lattice Carsten Rott Studied sensitivity of SFOFO lattice to imput beam parameters and cooling. Carsten will put his code, imput beam, and writup in the common code area. -cell description: 1 m long, with two bucking coils @ 77 A/mm^2 and 1 main coil @ 34 A/mm^2, 15 cm of liquid hydrogen absorber, 3 - 4 sections of RF, 8 T peak field. problems with cell description to be fixed by Carsten: ~ Be RF windows should be << 500e-6 m " Al windows on absorber -results and parameters: avg. E loss = 4.5 MeV/m, 1.5 MeV/gap 12 - 15 cm for RF power feed room for 1-2 more RF cells w/out changing lattice transverse emmitance 1200 mm-mmr optimum beta 15 cm RF phase 38 degrees RF @ 805 MHz peak voltage 36 MV field gradient 19.5 MV/m -conclusions: need to start with smallest possible beta at injection to lose as few particles as possible in first few cells. Problem is that low beta = large emittance growth at start. RF cooling behavior is very sensitively dependent on beam properties (esp. beta) at injection. correlation between E and amplitude IS necessary (contra Palmer claim) Carsten found that a channel optimized for cooling has bad beam transmission, and a channel optimized for transimission has no cooling. happy? middle ground: 30 % cooling after 15 cells, 5 % beam loss w/ beta = 20cm, phase = 32 degrees. Unfortunately, due to synchrotron amplitude, emmitance blows up after 15 cells. Following Discussion: -it would be nice to reproduce Palmer's result for SFOFO lattice. -code management: get LBL to release their SFOFO so at least we can get in tune with them, if not BNL too. STANDARDIZE -beam imput parameters. something like a card file in an event generator could work in Icool for imputting ~ parameters from a standardized list. -B field configurations Next step: 1) tune SFOFO channel @ emittance = 1500 mm=mr w/ more RF, then move to DPGeant and compare 15 T alternating solenoid and 8 T sFOFO results. 2) have Ed & Dan & Fla. look at sFOFO to see if fields are realizeable. ************************************************************************* * * * GOAL: * * * * End up with a paper comparing the two lattices, with * * engineering drawings, and studies of tolerances. * * * * * *************************************************************************