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Beamline MICE Analysis JUNE04 Including a proposal for a JUNE04A Configuration Tom Roberts Illinois Institute of Technology TJR August 2, 2004 MICE Beamline Analysis 1 JUNE04 Beamline Design Same basic physical layout as MAR04, with minor changes (e.g. downstream iron shield) Corrects many deficiencies of earlier designs JUNE04 still has problems: Beam distributions are not all as desired (see below) TOF0 singles rate is ~10 MHz Good mu+ rate is only about half of the desired 600 ev/sec This talk discusses my analysis of a number of suggestions to address these problems. I propose a JUNE04A design that both reduces the TOF0 singles rate and increases the good mu+ rate TJR August 2, 2004 MICE Beamline Analysis 2 JUNE04 Layout ISIS Beam TOF0 TOF1 Ckov1 Diffuser Iron Shield TOF2 Ckov2 Cal TJR August 2, 2004 MICE Beamline Analysis 3 JUNE04 Beamline Design Properties Attribute pion momentum muon momentum Diffuser Thickness (Pb) Design emittance after Diffuser, for 1% p/p g4bl/ecalc9f emittance after Diffuser, full momentum interval Good mu+ rate TOF0 Singles 350 MeV/c 250 MeV/c 8 mm y-y 6 mm-rad x-x >10 mm-rad 14.8 mm-rad 350 ev/sec 9.9 MHz Value TJR August 2, 2004 MICE Beamline Analysis 4 Observations on overall beam distributions, JUNE04 Average Momentum After Diffuser: 250MeV/c => ~ 236.5MeV/c Good for Amplitude vs p correlation Narrow-momentum (+/-1% ~ 236.5MeV/c): Beam OK = y RM S / y 'RMS 0.40 m R M S = ( ) y R M S y'R M S 6.1 m m ra d Narrow-momentum Beam OK xx' larger distribution (improvable with quad optics) Narrow momentum region yy' 6pi & well matched Overall beam distribution: Suffers from a few aberrations Full beam Still needs attention Peak Momentum > 236.5MeV/c ! TJR August 2, 2004 yy' 10pi & not well matched xx' large distribution, <x> 0 & not well matched 5 236.5MeV/c MICE Beamline Analysis Suggested Improvements Raise the pion momentum in the beamline o improve / separation in B2 o Reduce TOF0 singles by eliminating s o Slight increase in pion production Move TOF0 downstream of Q5, or downstream of Q6 o Reduce TOF0 singles o Reduce effect of multiple scattering in TOF0 o Requires moving TOF1 downstream of Q9, and an analysis that the pi/mu discrimination is still OK (below) Use thinner counters for TOF0 and TOF1 o Reduce effect of multiple scattering in TOF0 and TOF1 - Consider changing the tune from FDF in Q4-6 to DFD o Steer more pions into the Q4 iron, and away from TOF0 o Perhaps also DFD in Q7-9 o May be able to better balance the vertical and horizontal emittances (better horizontal aperture control of the beam?) Included in this analysis and proposal for JUNE04A TJR August 2, 2004 MICE Beamline Analysis 6 Evaluation Criteria At present we don t know the targeting parameters we will achieve, and basically must make an educated guess of what the overall rates will be. In practice, the target will have an adjustable insertion depth into the ISIS beam, and we will insert it until we are limited by one of the following: A. ISIS beam losses / activation of beamline elements B. Target heating C. Singles in TOF0 D. Tracker or DAQ event rate capacity The beamline design and tune cannot affect A, B, or D, and can only hope to optimize the good mu+ rate relative to TOF0 singles. The criteria I have used is to maximize the good- + rate and to minimize TOF0/good- +, both for a given set of 10M target +. Remarkably, these two criteria are compatible. TJR August 2, 2004 MICE Beamline Analysis 7 Proposed JUNE04A Layout P = 425 MeV/c Moved, Thinner, TOF0 Moved, Thinner, TOF1 New Iron Shield (TOF1 and its iron shield are symmetrical with TOF2, except for the Diffuser) 8 TJR August 2, 2004 MICE Beamline Analysis Comparison of JUNE04 Proposed and JUNE04A Attribute momentum (B1) momentum (B2) TOF0 position TOF1 Position TOF total thickness Upstream iron shield TOF0 to TOF1 distance TOF0 Singles Good + rate Design Emittance g4bl/ecalc9f emittance JUNE04 350 MeV/c 250 MeV/c Downstream of Q4 Downstream of Q8 2 inches None 8.5 meters 9.9 MHz 350 ev/sec 6 mm-rad [2] 14.8 mm-rad JUNE04A 425 MeV/c 250 MeV/c Downstream of Q6 Downstream of Q9 1 inch Same as downstream 7.8 meters [1] 3.8 MHz 512 ev/sec 6 mm-rad [2] 11.9 mm-rad [1] / /e discrimination in TOF1-TOF0 presented below. [2] Narrow-momentum beam, no multiple-scattering from TOF0 and TOF1, horizontal emittance much larger. Reasonably consistent with ecalc9 value. TJR August 2, 2004 MICE Beamline Analysis 9 JUNE04A / /e Discrimination in TOF1-TOF0 A major change in the JUNE04A design is the reduction in distance between TOF0 and TOF1, so we must verify that + can still be cleanly separated from + There are no protons TOF0 stops >99% of them in this momentum range Using Tracker1 to measure Ptot, the perfect-resolution graph looks fine: Perfect TOF and Tracker Resolution A Q4-filling Gaussian beam with equal numbers of +, + and e+ No correction for Eloss in the Diffuser GoodParticle = TOF0 & TOF1 & Tracker1 Still present: Variations in path length Variations in E loss (Diffuser) TJR August 2, 2004 MICE Beamline Analysis 10 Estimated TOF and Tracker Resolutions From the proposal, TOF0 and TOF1 are estimated to have resolutions of 50 ps, giving a resolution of 70.7 ps for TOF1-TOF0. From the proposal, Tracker1 is estimated to have a resolution in Pperp of 0.12 MeV/c. The resolution in Pz depends strongly on Pperp, and is given in Fig 3.9 of the proposal; it is modeled here: TJR August 2, 2004 MICE Beamline Analysis 11 JUNE04A / /e Discrimination, with Estimated Gaussian Resolutions in Pperp, Pz, and TOF TJR August 2, 2004 MICE Beamline Analysis 12 Conclusions about JUNE04A Straightforward modifications to JUNE04 provide significant improvements in performance: TOF0 singles reduced by a factor of ~2.5 Good + rate increased by a factor of ~1.5 Input emittance slightly reduced The reduction in TOF0 to TOF1 distance is OK we still have good / /e discrimination Reducing TOF0 and TOF1 to 1 inch total thickness improves the rate of good + Still need a design iteration: Improve horizontal distributions Correct the overall emittance Tune the Decay Solenoid field (better focusing and separation from ) TJR August 2, 2004 MICE Beamline Analysis 13 Comment on MICE Targeting Current Baseline ISIS Beam Ti Possible Change ISIS Beam 1 mm wide, 10 mm thick, variable depth 10 mm wide, 1 mm thick, variable depth There clearly is a multiple-scattering angle, and an energy loss, below which protons intersecting the target will not be lost. Because of this, it may be appropriate to rotate the target 90 degrees, so it is 10 mm wide and 1mm in length. While ~10 times more protons will intersect the target, perhaps only those that strongly interact will be lost. With everything else equal, we will adjust the depth so the number of strongly-interacting protons will be the same, independent of orientation. This might reduce ISIS losses, while not significantly affecting either the target heating or the MICE muon rates. MICE Beamline Analysis 14 TJR August 2, 2004 Comparison of 1mm and 10mm Target Thicknesses Multiple Scattering Energy Loss Clearly the 1mm-thick orientation has much less impact on individual ISIS protons than does the 10mm-thick orientation. Evaluating whether or not this target rotation will reduce ISIS losses requires an analysis using the ISIS beam properties and lattice. MICE Beamline Analysis 15 TJR August 2, 2004

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