CM Nov 2009 DOES MICE NEED STEP III ? Somewhat hard to understand MICE Schedule… –If the gods are (un)kind it’s possible that SS1, SS2 & FC1 are available at about the same time –May be savings in effort & time by skipping STEP III & going straight to STEP IV What are the differences? What would be lost? –STEP III.1 seemed desirable 1 – 2 years ago when funding for FC modules looked uncertain & schedule was different –Object is to stimulate (provoke) discussion

CM Nov 2009 STEPS III & III.1 Advertised purpose of Step III is ‘Control of systematics’ –What does that mean? Presumably compare both spectrometers with same muons –Presumably at central plane »Requires tracking through magnetic field »Propagation of errors on (x…, p x …) –This checks Trackers (and software) and alignment But Step III alignment is not same as Step IV, V, VI alignment –Spectrometer 2 will move each step –Error fields due to shield walls will be different Modest cooling could be demonstrated in STEP III.1 –For solid absorbers

CM Nov 2009 GEOMETRY OF STEP III / III.1 STEP III.1 has solid absorber – LiH, PE… a few mm between M2 Match coils

CM Nov 2009 GEOMETRY OF STEP IV FOCUS COIL MODULE 1520mm STEP IV ~ 700mm longer than STEP III Extrapolate tracks 350 mm further on each side Would this matter for comparison? Question for Tracker people (?) LH 2 Absorber – but maybe not initially Can use solid absorbers

CM Nov 2009 OPTICS OF STEP III Cooling could be measured in STEP III.1 –Optics not very favourable High (~72cm) beta at absorber Limited by 300A PSUs of Match Coils Non-standard (i.e. not design) currents in Match Coils –Next slide…. –50cm diameter LiH absorber in production

CM Nov 2009 STEP III MATCH COIL CURRENTS 167 A/mm^2 = 300 A = Current limit Not much overhead Perhaps some erosion of temperature margin ? MICE NOTE 158 MICE NOTE 199

CM Nov 2009 STEP IV OPTICS STEP IV is STEP VI without two AFCs & RFCCs –Same optics spectometer  absorber as steps V & VI –Beta = 42 cm at absorber (baseline 200MeV/c, flip mode) Better cooling than III.1 –But still quite modest –Match Coils operate at design currents STEP VI   STEP IV Beta (m)

CM Nov 2009 EMITTANCE GROWTH – STEP III Heating % Non Flip Mode Flip Mode Input Emittance (cm) (M. Apollonio CM14) Emittance grows – depending on beam emittance –e.g. 10mm beam grows by ~2.5% with no absorber Any result requires subtraction > raw effect Not very desirable

CM Nov 2009 EMITTANCE GROWTH STEPS III & VI Heating % Non Flip Mode Flip Mode Input Emittance (cm) (M. Apollonio CM14) Red points = STEP VI From MICE note 0244 Emittance also grows in empty STEP VI –10mm beam grows by ~2.7% with no absorber –Presumably the same in STEPS IV and V STEP IV never studied in detail –In any case, Amplitude Analysis (probably) fixes emittance growth problem for both STEPS III.1 and IV

CM Nov 2009 SUMMARY STEP III / III.1STEP IV Tracker/Spectrometer systematics Longer extrapolation to central plane. What do errors do? Question for Tracker group Optics & Cooling Modest at best Both steps require large subtraction (Amplitude may help) Higher beta function at absorber  Equilibrium Emittance higher by ~1.66 d  = – 3.8% maximum ~4.1% maximum even with LH 2 Longitudinal coolingNot consideredSolid wedge abs. studied MagneticsNon-standard currents in Match Coils; PSU limit ? Operates at design currents InstallationExtra Step to mount & demount before STEP IV LH 2 system may not be available immediately; Extra work to mount solid absorbers

CM Nov 2009 THE END