MICE

1. n International Muon Ionization Cooling Experiment p m MICE This talk: Measurements & measuring technique Next talk (Rob Edgecock): MICE – the UK Perspective.

2. A detector physicist view of MICE given a ~ 10 % cooling engine ..... a mysterious black blox .... build for it an unequivocal ~ 1% “diagnostics” tool two complete (almost) identical detectors (two spectrometers equipped with timing & PID) one in front of and one in the back of the box each providing a complete measurement of all six parameters of each particle to measure the beam emittance both in & out of the box i.e. the ~10% emittance reduction with ~ 1% uncertainty i.e. with an absolute error equal to 0.1%

3. Quantities to be measured in a cooling experiment cooling effect at nominal input emittance ~10% equilibrium emittance curves for 21 MV, 3 full absorbers, particles on crest  both output emittance & transmission decreases ...better FOM needed

4. Quantities to be measured in a cooling experiment (ctd) number of particles inside acceptance of subsequent accelerator (for nominal NuFact, 15 mm rad, 30%) Need to countmuons coming in within an acceptance box and muons coming out. must not only measure emittances, but also count particles It is difficult to count very precisely particles of a given type in a bunch and to measure emittance very precisely. => single particle experiment

5. Emittance measurement Each spectrometer measures 6 parameters per particle x y t x’ = dx/dz = Px/Pz y’ = dy/dz = Py/Pz t’ = dt/dz =E/Pz Normalized emittance n by using (x, y, t, p/mc.dx/dz, p/mc.dy/dz, p/m.dt/dz) Determines, for an ensemble (sample) of N particles, the moments: Averages <x> <y> etc… Second moments: variance(x) sx2 = < x2 - <x>2 > etc… covariance(x,y) sxy = < x.y - <x><y> > Covariance matrix M = Getting at e.g. sx’t’ is essentially impossible with multiparticle bunch measurements Compare ein with eout Evaluate emittance with:

6. Single particle experiment • => truely thorough analysis • Correlationsbetween phase space parameters can be easily measured. • The detailed understanding of the role of each beam parameter • energy • transverse momentum • RF phase (=time) • ............ • can easily be studied by making selection cuts in the ensemble. A wide range of parameters being sampled, any desired input beamconditionscanbereconstructed by appropriate slicing and/or reweighting of the population of particles observed.

7. requirements on detector system: • tageach particle considered: selectmuon, in & out ! • in…… reject e, p, p • => TOF2 stations 10 m flight with 70 ps resolution • &up-Cerenkov, if life were tough • out…… reject e => down-Cerenkov + em Calorimeter • 2. measure all6 particleparameters • i.e. x,y,t, px/pz , py/pz ,E/pz • 3. each withresolution 10% ( 1% in quadrature) • of width around equilibrium emittance … • … ieadequate to preserveunsmearedestimates • ofvariances & covariances .. emittance !!! • 4. standpossibly severe noise level fromRF cavities

8. 10% cooling of 200 MeV muons requires ~ 20 MV of RF single particle measurements => measurement precision can be as good as D ( e out/e in ) = 10-3 never done before either…. Coupling Coils 1&2 Spectrometer solenoid 1 Matching coils 1&2 Matching coils 1&2 Spectrometer solenoid 2 Focus coils 1 Focus coils 2 Focus coils 3 m Beam PID TOF 0 Cherenkov TOF 1 RF cavities 1 RF cavities 2 Downstream particle ID: TOF 2 Cherenkov Calorimeter Diffusers 1&2 Liquid Hydrogen absorbers 1,2,3 Incoming muon beam Trackers 1 & 2 measurement of emittance in and out

9. need ofsimplymatching with the cooling section and of keeping a large-emittance beam in a small physical volume =>solenoidalspectrometercoaxial to cooling channel Blondel, Janot 01 two “timing helicometers” Each measures, very precisely, &time stamps the helicoidal trajectory of each individual muon Each a precisetracker device inside a 4 T solenoidal magnetic field matching the transverse diameter of the muon beam being cooled (30 cm) capable also of precise (70 ns) timing Difference is in the PID systems emphasis on p/m separation in front of the front detector fighting beam contamination on m/e separation in the back of the back detector fighting muon decay

10. Tracking & timing the helices need ofsimplymatching with the cooling section keeping a large-emittance beam in a small physical volume => chose solenoid magnets coaxial to the cooling channel Blondel, Janot 01 B Field (x,y) measurements at 3 different z values in principle sufficient length such that average makes about (2/3 of) a turn ie about 1 m for 200 MeV/c in a 4 T solenoid 70 ps TOF measures phase of  to 5° wrt the 201 MHz RF

11. TRANSVERSE MOMENTUM RESOLUTIONspt = 110 keV Performance Pt/Pz E/Pz  0.06 % resolution Pz resolution degrades at low pt : resolution in E/Pz is much better behaved  0.06 % resolution measurement rms is 4% of beam rms … also ≈100 m spatial resolution real small

12. MICE simulations & general sofware effort A fast simulation (DWARF4), including dE/dx & MS, was used for the basic design ….. emittance generation tracking particle identification ................ since the time of the LOI A more complete GEANT4 simulation (G4MICE) long term foundation of the MICE sofwtare, including everything • true end-to-end simulation of BOTH cooling AND detectors • complete description of the detectors, down to digitization • first repository of reconstruction algorithms now already providing first results

13. background fromthe nearby high-gradient RF cavities solenoidal geometry... one major drawback fortrackers exposed almostdirectly to a large dark current and x-ray background however i) background moderate at RF gradient of 8.3 MV/m baseline due to limited availability of RF power ii) LiH absorbers do absorb dark current e-completely, only x-rays only through iii) the detectors are built of low-Z material x-raysCompton hits are less frequent & distinguishable from  triplets it appears that the performance of the detectors will not be affected studies of this background continue .... with high priority! did we ever have the RF power ...

14. Estimating the background measure 4 x 104 Hz/cm2e rate at 8 MV/m in lab G 805 MHz pillbox cavity scaling to 201 Mhz by the volume ratio of cavities (emitter area proportional to surface, energy to length) gives total e rate of 30 MHz for detector radius 15 cm (an area of 700 cm2) converted to photons by absorber (efficiency = Re/X0~ 0.07) Re e range, X0 rad length 0.26% Compton scatters in the detector per plane 6 fibre ribbons 0.035 cm thick X0 45 cm rate about 0.5 MHz/plane (admittedly large uncertainty) about 2-3 orders of magnitude below levels found tolerable by G4MICE studies ... while materials & surface treatments also being investigated

15. Backgrounds real background reduced by factor L/X0(H2) . L/X0(det) 0.07 0.0026 measured dark currents • Extrapolation to MICE (201 MHz): • scale rates as (area.energy) X 100 • and apply above reduction factor 2 10-4 • 4 104 Hz/cm2 @ 8 MV/m @805 MHz • 0.8 kHz/cm2 per sci-fi • 500 kHz/plane ! within  one order of magnitude ! Dark current backgrounds measured on a 805 MHz cavity in magnetic field with a 1mm scintillating fiber at d=O(1m)

16. => 6.70 MV/m => 4.65 MV/m .43 X 4 cells = 1.7 m  11.5 MV for 1X 4 = 6.70 MV/m 16 MV for 2X4 = 4.65 MV/m 16 MV for 1X4 = 9.3 MV/m

17. Tracker Baseline Option: Sci Fi tracker – 5 stations with 3 crossing double planes of 350 m fibres readout by VLPC (High Q.E. and high gain) as in D0. Pro: we are essentially sure that this will perform well enough for MICE. Con: 43000 channels make it quite expensive (4.1 M€) 2 cost saving alternatives, under energic investigation : Option 1Sci-Fi -- Reduce channel count by multiplexing channels (1/7) Pro: cheaper by factor 4. Con: less sure to work in presence of Bkg and a few dead channels. Option 2 Use a Helium filled TPC with GEM readout (‘TPG’) Pro: very low material budget (full TPG = 2 10-4 X0) and lots of points/track (100) cheaper (<0.5 M€ of new money) Con: long integration time (50 ms vs 10 ns) => several muons at a time + integrated noise effect of x-rays on GEMs themselves unknown.

18. Tracker Baseline Option: Sci Fi tracker – 5 stations with 3 crossing double planes of 350 m fibres readout by VLPC (High Q.E. and high gain) as in D0 … see MUSCAT also Pro: we are essentially sure that this will perform well enough for MICE. Con: 43000 channels make it quite expensive, if read out individually (4.1 M€)

19. Sci-Fi studies with G4MICE concept background simulated 1000 times larger that extrapolated from measurements does NOT degrade resolution seriously (No multiplexing here!) further improvements from the RF cavity will be seeked (TiN coating) etc… looks good. if this is confirmed, one could envisage running with higher gradients. This is possible if -- 8 MW power to one 4-cavity unit -- LN2 operation in out

20. Cost saving alternatives: Option 1 MultiplexSci-Fi -- Reduce channel count (1/7) Seven 350 m fibres multiplexed by a 7:1 multiplexing wave guideinto one VLPC pixel. only be about a 10% loss of light in the outer ring of fibres due to a slight mismatch. Pro: cheaper by factor 4 …. save 3 M !!!!! Con: less sure to work in presence of bkgd and of a few dead channels. OK if backgrounds from the RF cavities stays at a low level

21. Cost saving alternatives: Option 2 TPG ………… a 90% Helium filled TPC1 m long and 30 cm Ø Novel: GEM amplification and hexaboard R/O Pro: very low material budget (full TPG = 2 10-4 X0) lots of points/track (>100) oustanding pattern recognition cheap (<0.5 M€ of new money) Con: long integration time (50 ms vs 10 ns) => several muons at a time + integrated noise effect of x-rays on GEMs themselves …. still to be ested

22. at noise rate similar to that simulated for fibers, no difficulty finding tracks and measuring them. resolution somewhat better than sci-fi (which is good enough) difficulty: nobody knows the effect of RF photons on the GEM themselves tests in 2003, decision October 2003

24. basic TOF design : upstream t0tintout 1212 4040 cm2 trigger ... simple doubles & triples .... 70 ps rms ..... 1%p/m ID ( 1400 ps TOF ..) + 5° timing wrt the RF phase TOF0 BicronBC-420 plastic scintillator Hamamatsu R4998 PMTs TOF1&2 BC-404 fine mesh Hamamatsu R5505 OK in 1 Tesla fringe fields thou reduced gainBESS] + dedicated laser calib system[HARP]

26. Particle Identification Both residual beam pions and muon decay electrons fake different kinematics spoil and biasthe emittance measurements must have < 0.1% of either in the sample PID rejection must be strong & redundant both up and down stream

27. Upstream Particle Identification Even with a solenoid decay channel, the beam is not pure. Entering electrons and protons have different cooling properties and must be rejected (easy) Pions are more of a problem since they candecay in flight with a daugther of different momentum ………………. big bias in emittance! need less than 1 ‰ pion contamination in final sample. TOF in the beam line with 10m flight path and 70 ps resolution provides p/mseparation better than 1% @ 300 MeV/c (t = 1400 ps ! )  it is sufficient that the beam has fewer than 10% pions A small beam Cherenkov is foresen to complete the redundancy in this system (overlaps …. or higher p/m …) a 5 ” Ø vessel of liquidC6F14(n=1.25), 30 cm long in total

28. Downstream PID 0.5% of  decay in flight ………… large bias if a forward-decay e is kept as  two systems are foreseen to get to eliminate electrons below 10-3 : Electromagnetic Calorimeter (mip = em shower 27 MeV, use also z profile) Aerogel Cherenkov ( n=1.02,  blind , threshold well above beam momentum ) Positive Identification of a particle in the calorimeterconsistentwitha muon ANDno electron signal in the Cherenkov

29. PRECISION • statistical errors • --emittance is measured to 10-3 with ~106 muons. • -- ratio of emittances to same precision requires much fewer (105)a nice unexpectedsurprise • (re)measuring again the same  , after little material • … in & out strongly correlated • statistical fluctuations largely cancel in the ratio • -- Due to RF power limitations we canrun about 10-3 duty factor 1ms/s • -- To avoid muon pile up we want to run at ~1 muon per ISIS bunch (1/330ns) • 3000 muons /s • -- The emittance generation must cover cooling acceptance uniformly • -- 25% of incoming muons within acceptance • -- about 1/6 mimic a bunch on crest => MICE cools 100 muons/s . • A 10-3 measurement of emittance ratio will take 103 s … 1/3 hour !! • N.B. this assumes a beam line with a solenoid to be obtained from PSI. • A quadrupole channel has more background and less rate, and would lead to a time longer by a factor ~10.

30. statistical errors • --emittance is measured to 10-3 with ~106 muons. • --ratio of emittances to same precision requires much fewer (105) • a nice surprise, unexpected • measuring again the same , after little material • … in & out strongly correlated • statistical fluctuations largely cancel in the ratio • -- To avoid muon pile up we want to run at ~1 muon per ISIS bunch (1/330ns) • 3000/s • -- The emittance generation must cover keeps • 25% of incoming muons within acceptance • about 1/6 are on crest … a bunch … => 100 good muons per second. • -- Due to RF power limitations we can run about 10-3 duty factor 1ms/s • A 10-3 measurement of emittance ratio will take 106 s < one hour • N.B. this assumes a beam line with a solenoid to be obtained from PSI. • A quadrupole channel has more background and less rate, and would lead to • a time longer by a factor ~10.

31. ACCURACY systematic errors MICE-FICTION: . MICE measures e.g. (eout/ ein)exp = 0.894 ± 0.001 (statistical) compares with (eout/ ein)theory. = 0.885 and tries to understand such a~ 0.01 difference in emittance reduction SIMULATION B. experimental systematics: modeling of spectrometers is not as reality A.theory systematics: modeling of cooling cell is not as reality REALITY MEASUREMENT

32. No systematic must affect the expected 10% cooling effect by more than 10–3 absolute, i.e., 1% of its value. The errors of class A (modeling the cooling cell) Errors in this category include: ·Uncertainties in the thickness or densityof the liquid-hydrogen absorbers and other material in the beam ·Uncertainties in the value and phase of the RF fields ·Uncertainties in the value of the beta function at the location of the absorbers Misalignment of the magneticelements Uncertainty in the beam energy scale Uncertainties in the theory (M.S. and dE/dx and correlation thereof) All errors of type A become more important near the equilibrium emittance. The errors of class B (modeling the pair of detectors ): systematic differences between incoming and outgoing measurement devices different efficiency different misalignments possible differences in the magnetic field of the two spectrometers will constrain them heavily .... got a full arsenal of ancillary measurements Step III or run MICE empty with no RF or analyse cooling vs muon phase (free)or .....

33. Most critical is the control of the magnetic fields. For this reason MICE will be equipped with a set of magnetic measurement devices that will measure the magnetic field with a precision much better than 10–3. Magnetic measurements design of system and procedures by Saclay (Rey, Chevallier) NIKHEF will provide the probes (Linde)

34. m - STEP I: 2004 STEP II: summer 2005 STEP III: winter 2006 STEP IV: spring 2006 STEP V: fall 2006 STEP VI: 2007 full power

35. The statistical precision will be very good and there will be many handles against systematics. We believe that the systematic errors on the measurement of the ratio of emittances can be kept below 10-3 This will require careful integration of the acquisition of data from the spectrometers and from the cooling cell. A lot remains to be done in this area, admittedly, to make sure that MICE has foreseen the necessary diagnostics by the time it turns on.

38. Next Future • Prototype critical detectors (trackers) in 2003 • Test beds … Fermi … KEK …. CERNPS … • bkgrounds • …… Sci Fi • …..TPG • 2. Choose   helicometer option Oct 31 (CollMeet) • 3. Start build late this year … more standard items • ………trigger&TOF, PID subdetectors • 4. Be there first …. • …. well understood by the time • the cooling engine arrives

39. Conclusions The MICE detector system an integrated tool … a pair of challenging particle detectors… capable to measure reduction of emittance at 1% level appears feasible first to be studied a full cell of the US NuFact design studyII including a number of beam & optics conditions beyond the baseline The collaboration has organised responsibilities, determined the basic costs and time line of the construction and commissioning of the two detectors .

40. requirements on detector system: • tageach particle considered: selectmuon, in & out ! • in…… reject e, p, p • => TOF2 stations 10 m flight with 70 ps resolution • &up-Cerenkov1/2” Ø,30 cm liquidC6F14 (n=1.25) cell • out…… reject e => down-Cerenkov + em Calorimeter • 2. measure allits six parameters • i.e. x,y,t, px/pz , py/pz ,E/pz • 3. each withresolutionbetter than 10% of • width at equilibrium emittance (correction less than 1%) … • … ieadequate not to smear (spoil sensitivityto) • variances & covariances …... emittance !!! • 4. Berobust againstnoise fromRF cavities

41. Further Explorations We have defined a baseline MICE, which will measure the basic cooling properties of the StudyII cooling channel with high precision, for a moderate gradient of ~8 MV/m, with Liquid Hydrogen absorbers. Many variants of the experiment can be tested. 1. other absorbers: Various fillings and thicknesses of LH2 can be envisaged The bolted windows design allows different absorbers to be mounted. 2. other optics and momentum: nominal is 200 MeV/c and b = 42 cm. Exploration of low b (down to a few cm at 140 MeV/c) Exploration of momentum up to 240 MeV/c will be possible by varying the currents. 3. the focus pairs provide a field reversal in the baseline configuration, but they have been designed to operate also in no-flip mode which could have larger acceptance both transversally and in momentum (Fanchetti et al) (We are not sure this can be done because of stray fields…) 4. Higher gradients can be achieved on the cavities, either by running them at liquid nitrogen temperature (the vessel is adequate for this) (gain 1.5-1.7) or by connecting to the 8 MW RF only one of the two 4-cavity units (gain 1.4)

42. Time Lines … to be reformulated Time lines for the various items of MICE have been explored – procurement delays and installation – the critical items are solenoids and RF cavities. If funding is adequate, the following sequence of events can be envisaged * -> consistent with the logistics of the beam line upgrade at RAL and of the various shut downs. Muon Ionization cooling will have been demonstrated ands measured precisely by 2007 At that time MINOS and CNGS will have started and mesured Dm132 more precisely J-Parc-SK will be about to start up (Q13) LHC will be about to start as well It will be timely (…and not too soon!) to have by then a full design for a neutrino factory, with one of the main unknowns (practical feasibility of ionization cooling) removed.

43. m - STEP I: 2004 STEP II: summer 2005 STEP III: winter 2006 STEP IV: spring 2006 STEP V: fall 2006 STEP VI: 2007