K.Walaron Fermilab, Batavia, Chicago 12/6/ Simulation and performance of beamline K.Walaron T.J. Roberts

K.Walaron Fermilab, Batavia, Chicago 12/6/20062 G4beamline: An overview G4beamline is code based on full GEANT4 implementation. G4beamline is code based on full GEANT4 implementation. Very realistic. Very realistic. All stochastic physics, decays, quads and dipoles realistic. Fringe fields included. All stochastic physics, decays, quads and dipoles realistic. Fringe fields included. Decay Solenoid  Field map, Tracker Solenoid  Opera 2D field map. Decay Solenoid  Field map, Tracker Solenoid  Opera 2D field map. All materials included, windows realistic, world volume is air. All materials included, windows realistic, world volume is air. Anything that should be in vacuum is in vacuum e.g. except for air- gap to decouple ISIS/pion-channel everything is in vacuum until end of decay solenoid. Anything that should be in vacuum is in vacuum e.g. except for air- gap to decouple ISIS/pion-channel everything is in vacuum until end of decay solenoid. Point to make is that we believe the G4beamline simulation is accurate to a good level and is a powerful tool for beamline evaluation Point to make is that we believe the G4beamline simulation is accurate to a good level and is a powerful tool for beamline evaluation

K.Walaron Fermilab, Batavia, Chicago 12/6/20063 Target/beamline interface ISIS beam profile not well known ISIS beam profile not well known ISIS beam-loss constraints ISIS beam-loss constraints Assumptions have been made to best of knowledge Assumptions have been made to best of knowledge Target test in Oct ’06 will improve knowledge Target test in Oct ’06 will improve knowledge Identified as area where lack of knowledge exists. Low impact on optics design, possible impact on rates. High impact if we trip ISIS but target depth will be variable. Target test should illuminate this (no pun intended). Identified as area where lack of knowledge exists. Low impact on optics design, possible impact on rates. High impact if we trip ISIS but target depth will be variable. Target test should illuminate this (no pun intended).

K.Walaron Fermilab, Batavia, Chicago 12/6/20064 Target/beam assumptions Target materialTitanium Overall target height10 mm Target height intersecting ISIS beam2 mm Target width1 mm Target length along beam10 mm Target fraction of an interaction length0.036 ISIS total beam area at target4400 mm 2 ISIS relative beam density at target (edge of beam) 10% Target insertions per second1 Target duration in beam with good RF1 ms ISIS protons/bunch2.5·10 13 ISIS bunch rate at target1.5 MHz Protons intersecting target during 1 ms with good RF 1.7·10 12

K.Walaron Fermilab, Batavia, Chicago 12/6/20065 Rate normalisation method 3 separate target simulations: MARS, GEANT4, LAHET For each outgoing π+ determine its polar angle, and weight it according to the azimuth fraction of 360° that the polar angle intersects the angular acceptance rectangle of MICE. Sum the weights for all pions within the momentum cut Tune shown: Momentum acceptance of 427<Ptot<461 DescriptionLAHETMARS Protons on target1.000·10 7 π + weighted into acceptance π + per second into acceptance 5.64· ·10 5 π + generated into acceptance and tracked 1.000·10 6 good μ + tracked (no LH 2, no RF) 1737 good μ + per millisecond

K.Walaron Fermilab, Batavia, Chicago 12/6/20066 Beamline Optics tune method Select momentum acceptance Select momentum acceptance Magnet currents defined using turtle/transport Magnet currents defined using turtle/transport Tune both dipoles: Stochastics off, reference particle down beamline centre Tune both dipoles: Stochastics off, reference particle down beamline centre For higher/lower momentum tunes scale currents For higher/lower momentum tunes scale currents

K.Walaron Fermilab, Batavia, Chicago 12/6/20067 CM15-6pi-200MeV/c example evaluation π+ central momentum (B1) MeV/c μ+ central momentum (B2) MeV/c μ+ mean momentum in Tracker1 – design 206 MeV/c μ+ mean momentum in Tracker1 – achieved 221 MeV/c* Diffuser thickness (Pb) 0.95 cm Design input emittance 6 π mm-rad * Peak in distribution does appear to be ~206 MeV/c. High momentum tail accounts for the higher mean

K.Walaron Fermilab, Batavia, Chicago 12/6/20068 Tracker1 beam profiles

K.Walaron Fermilab, Batavia, Chicago 12/6/20069 Muon matching section beam envelopes Envelopes are the RMS of the sub- distribution of mu+ in the energy range < E mu+ <252.2

K.Walaron Fermilab, Batavia, Chicago 12/6/ D normalised emittance TOF0 and CKOV1 TOF1 Diffuser (9.5mm) mu+ in the energy range < E mu+ <252.2

K.Walaron Fermilab, Batavia, Chicago 12/6/ Singles Rates and particle contamination Descripti on LAHET singles (MHz) MARS singles (MHz) Average renormal ised singles (MHz) TOF CKOV TOF Tracker1 (1 st plane) Good mu ParticleTOF1 p0.45% π+π+ 1.29% μ+μ+ 97% e+e+ 0.03% n0.06% γ0.03% π-π- 0 μ-μ- 0 e-e- 0 Anti nu_mu1% Nu_mu0.07% Nu_e0.04%

K.Walaron Fermilab, Batavia, Chicago 12/6/ Matching We are certain that we can produce the 3x3 matrix of beam configurations (1pi is a problem) Matching into the MICE tracker important Want to match ptot design +/- 10% distrubution to desired twiss parameters inside tracker Identified as a risk and recent provision made to study this. Optimiser under development to match to beta function by altering 6 muon channel quadrupoles Initial studies show, for example, for this tune the following results Q4 Q5 Q6 Q7 Q8 Q9 beta betaDiff 4Demitt