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MICE magnetic measurements : AFC considerations Alain Blondel

MICE magnetic measurements : AFC considerations Alain Blondel. see a previous discussion for reference in CM35 ( Feb 2013 slides by V. Blackmore , A. Blondel ( presenter ) , J. Cobb, et al) http://indico.cern.ch/event/222409/session/0/contribution/39/material/0 /.

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MICE magnetic measurements : AFC considerations Alain Blondel

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  1. MICE magneticmeasurements: AFC considerations Alain Blondel see a previous discussion for reference in CM35 (Feb 2013 slides by V. Blackmore, A. Blondel (presenter) , J. Cobb, et al) http://indico.cern.ch/event/222409/session/0/contribution/39/material/0/

  2. from the feb’13 slides Motivations for magneticmeasurements 0. PrecisionIn order to understand the coolingmeasurements (and the multiple scattering and energylossmeasurements) specially in case of discrepancybetween the predictions and the experimentalresults the magneticfieldrequiredprecisionis of the order of a few gauss. 1. Focus coils:magneticmeasurements of focus coils are aimedat the determination of the intrinsicproperties of the magnetssuch as alignment and symmetry of the coils, possible difference in expectations betwween flip and non flip mode due to different forces, etc… the measts in R9 serve as reference in an environment which is reasonably iron-free. The measurements in the hall in situ (with the exact samesequences of points) serve to measure the field and itsstrayfield as well as probe the understanding of the effect of magnetic masses in the hall. This comparisonwillbeavailable for the AFC only. 2. Spectrometer solenoids These magnets are part both of the measurement and of the cooling channel (matching coils) The magnetic measurements serve two purposes: 1) to allow precise reconstruction of particle momentum in the tracker, and 2) as above, to allow precise understanding of the particle transport for the cooling and absorber propertiesmeasurements. It is important that the measurementstake place with the magneticenvironment (Virostek Plates on etc…) and preferably in the MICE hall (possible distortions due to magnetic masses)

  3. Preamble and correction: with the Magneticyoke in place, measurements of magneticfield in the MICE hall becomequiteunpractical. In addition the question of ‘unknownmagnetic masses’ ismoot, beingreplaced by the question: how well do we know the effect of large knownmagnetic masses? Nevertheless the magneticmapping of the MICE magnetsis essential -- detailedfieldmapscanfindunexpecteddefects in magnet construction -- in the case of the FC the map in solenoid mode and flip mode addressmagnetswith large and different forces (actually, forces at the twoextremes of the possibilities)  the motivation for measurements ‘in situ’ isweakened ... but the question «how preciselycanwe deal with the return yoke?» remains open.

  4. constraints 1. AFC1 onlyreachesjust 188 A (~200 MeV/c at 42 cm beta) is up and runnig 2. AFC2 workedpoorly but couldbemuchbetterafter fixes. 3. It isplanned to test AFC2 to see if wepreferit for step IV running itisplanned to arrive at RAL 4. Twoweks of fieldmappingcouldtake place between Monday 5th May and Friday 16th May.  5. it is planned in any case to test switch over from Focus mode to sol mode and vice versa to see how much time this takes.

  5. FC magnetismeasurements in R9 as planned in February 2013 minimal set and minimal time Sequence 1 -A: empty FC, Flip mode +- upstream Sequence 1 -B: empty FC, Flip mode+- downstream Sequence 1 FC Measurementdevice 1 for FCs  suggestwe do 1-A, 1-B, 1-C and 1-D .. ... if time permits. Allow 7 days for 1-A and 1-B day 1 preparations day 2 fine setting, survey <150m) 1st measurements and check day 3 measurements 1-A day 4 move to 1B and survey day 5 measurements day 6+7: reserve a few days for polarity change 5 days for 1-C and 1D  3 weeks Sequence 1 -D: empty FC, Sol mode ++ upstream Sequence 1 -C: empty FC, Sol mode++ downstream

  6. Measuringmesh: AFC scan settings assume 10 seconds per point sequence 1-B or 1-C: the extention of 40cm allowsmeasurement wellpast the flange This needs to beupdated to takeintoaccount Flip mode: 0, 50% 100% Sol mode: 0% 100% 1.2m 20cm 60cm scan steps as of Feb ‘13: 1. within the magnet and in nearstrayfieldregions (80cm): 16 phi steps, every 2cm in z  640 points time = 1.8rs 2. in outerfieldregion (120cm) 16 phi steps, every 5 cm in z  384 points time = 1.1hr magnet settings 1/3 , 2/3, and full field (114 for solenoid mode, 225 in flip mode) total measuring time = 9hrs for simplicity in analysis all settings willbemeasuredwith the samemeasuringmesh

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