27/6/05 Frascati1 M. Bonesini INFN Milano A possible design for MICE TOF stations

27/6/05 Frascati2 Outline  Introduction  Considerations on environment  TOF stations design  Some simulation results  PMTs tests  Ideas for the calibration system  Preliminary cost estimate  Conclusions

27/6/05 Frascati3 Aim of TOF stations TOF0 experiment trigger TOF0/TOF1 PID on incoming muons TOF1/TOF2 PID on particle traversing the cooling channel Requirements: oSingle detector resolution  ~60 ps oHigh rate capability oSustain nearby B fringe fields

27/6/05 Frascati4 TRD SEPT04 Layout TOF0 TOF1 Ckov1 Iron Shield TOF2 Ckov 2Cal ISIS Bea m Diffuser Proton Absorber Iron Shield

27/6/05 Frascati5 …MICE ToF0 Cherenkov Calorimeter Focus Coils Coupling Coils Liquid Hydrogen Absorbers RF Cavities Tracking Spectrometers Matching Coils Beam Diffuser Tof1 Tof2

27/6/05 Frascati6 The environment The beamline design puts harder and harder requests on TOF stations Higher and higher particle rates ( now MHz for TOF0, it was ~1 MHz at beginning) Request for thinner and thinner scintillators (to reduce multiple scattering) TOF stations in the fringe field of magnets: quadrupoles for TOF0 (B ~ gauss), solenoids for TOF1/TOF2 (B~.2 T)

27/6/05 Frascati7 Summary of Rates (Sept04 from Tom Roberts) DescriptionLAHETGeant4MARS TOF TOF Tracker Tracker TOF Good μ Values are events per millisecond of Good Target; absorbers empty, no RF. Good μ + = TOF0 & TOF1 & Tracker1 & Tracker2 & TOF2 & TOF1(μ + ) & TOF2(μ + ) Major changes from before: 2 in. total thickness of TOF0 and TOF1  ~20% reduction in Good μ+ ~50% larger target acceptance  ~10% increase in TOF0 singles, ~1% in Good μ +.

27/6/05 Frascati8 TOF Detector Layout TOF X/Y planes with PMTs at both ends: TOF0 is placed after Q6.  TOF1 is placed after Q9.  TOF2 downstream Transverse sizes:  TOF0,1,2 are all 48  48 cm. Segmentation:  All stations are 2 planes arranged orthogonal to each other.  TOF0 has 12 slabs in each plane. NO OVERLAP (to cope with higher rates)  TOF1,2 have 8 slabs per plane. NO OVERLAP TOF0 environment: Low field: g; High rate: 2.5 MHz. TOF1,2 environment: High field: 1-2 Kg; Medium rate 0.5 MHz

27/6/05 Frascati9 Problems for high resolution scintillator based TOF (  t < 100 ps)  pl dominated by geometrical dimensions  (L/N pe )  scint  ps (mainly connected with produced number of  ’s fast and scintillator characteristics, such as risetime) choice BC404  PMT dominated by PMT TTS (160 ps for R4998) Additional problems in harsh environments: 1.B field (shielding?) 2.High incoming particle rates

27/6/05 Frascati10 Considerations on scintillator thickness Shown time resolution is FWHM vs scintillator thickness L Green/red lines from BC408; blue line is BC404 (faster) Data from MEG tests at BTF Thin solution:  100 ps if all goes right (perfect detector calibration,...) I will retain thick solution (1” slabs) Actual choice :  60 ps

27/6/05 Frascati11 Some simulation studies: TOF0 TRD Size 480x480

27/6/05 Frascati12 TOF0 X/Y singles projection With 4 cm width slabs max counter rate seems < KHz. R4998 maybe OK with booster or active divider circuit (studies under way)

27/6/05 Frascati13 Transit Time for Upstream Tof Planes Transit time between Tof0 and Tof1 Quad fields are currently ignored Pions and muons can be distinguished

27/6/05 Frascati14 Downstream PID (from Rikard) good (No Ckov2)

27/6/05 Frascati15 Single scintillator counter layout BC404 scintillator (compromise between cost and performances: decay time 1.8 ns, att length~ 160 cm, max emission at 408 nm well matched with R4998 max response at 420 nm) L=480 mm to avoid particles hitting lightguides W=40 mm to reduce rate with a sensible counter number T=1” to have good timing resolution

27/6/05 Frascati16 Mechanics for TOF0 View of X/Y plane: 12 vertical counters, 12 horizontal counters

27/6/05 Frascati17 TOF0 support structure

27/6/05 Frascati18 Considerations for TOF0 PMT choice 1. Rate capability (up to some MHz) 2. Good timing properties (TTS) 3. Sustain magnetic field (we now assume <50 gauss for TOF0)

27/6/05 Frascati19 PMT test setup Laser source to simulate MIP signal (about 300 p.e.) : fast AVTECH pulser AVO-9A-C (risetime 200 ps, width ns, repetition rate 1KHz-1MHz) with NDHV310APC Nichia violet laser diode(~400 nm, 60 mW) NEW!! fast PLP-10 laser on loan from Hamamatsu Italia Laser sync out triggers VME based acquisition (TDC + QADC) // MCA SILENA system Home made solenoid test magnet (B up to 50 gauss, d~20 cm, L~50 cm) see later for details

27/6/05 Frascati20 Rate capabilities of PMTs To have a linear signal the mean average anode current (100  A for R4998 ) must not be exceeded -> damage to dynodes... shorter PMT lifetime This gives a theoretical rate capability of: 267 KHZ with R4998 BUT !!! Divider can be modified for R4998 (going up to 1.67 MHZ) with booster or active divider

27/6/05 Frascati21 Solenoid test magnet (B up to 50 gauss) Test solenoid, PMT inside Avtech pulser Laser diode

27/6/05 Frascati22 Used laser light source (PLP 10) Light source: Hamamatsu fast laser (  405 nm, FWHM 60 ps, 250 mW peak power) PLP-10 Optical system: x,y,z flexure movement to inject light into a CERAM/OPTEC multimode fiber (spread 14 ps/m) PMT under test Laser light Signal ~ 300 p.e. to reproduce a MIP as measured with an OPHIR Laser powermeter

27/6/05 Frascati23 R4998 PMT rate studies R4998 with modified divider circuit: booster for last dynodes Nominal: up to 1.5 MHz

27/6/05 Frascati24 Gain in magnetic field for R4998 Y x Z 50 gauss

27/6/05 Frascati25 Timimg properties of R4998 in B field

27/6/05 Frascati26 Rate effects studies for R4998 done with available R4998 with modified divider from Hamamatsu (booster on last dynodes) Light signal corresponds to ~ 300 p.e. 1 MHz

27/6/05 Frascati27 Considerations for TOF1/TOF2 PMT choice 1. Rate capability (up to some MHz) 2. Good timing properties (TTS) 3. Sustain magnetic field ( about gauss for TOF0, about.2 T for TOF2) Tests at Lasa magnet test facility (end July 04, for 15 days) with Pavia MEG group to optimize choice (M.Bonesini, F.Strati INFN Milano, G.Baccaglioni,F.Broggi, G. Volpini INFN Milano –LASA, G. Cecchet, A. DeBari, R. Nardo’, R. Rossella INFN Pavia).

27/6/05 Frascati28 Tests done at LASA Laser source to simulate MIP signal (about 300 p.e.) : fast PLP-10 laser on loan from Hamamatsu Italia Laser sync out triggers VME based acquisition (TDC + QADC) 5000 events for each data point : different PMTs (fine-mesh vs mod R4998), different B- field, different inclination vs B field axis (  ), diff laser rate to simulate incoming particle rates

27/6/05 Frascati29 Test magnet at LASA (B up to 1.2T) PMT under test 1.B field up to 1.2 T 2.Free space 12 cm in height

27/6/05 Frascati30 Fine Mesh Photomultiplier Tubes Secondary electrons accelerated parallel to the B-field. Gain with no field: 5 x 10 5 – 10 7 With B=1.0 Tesla: 2 x x 10 5 Prompt risetime and good TTS Manufactured by Hamamatsu Photonics R5505R7761R5924 Tube diameter1”1.5”2 “ No. Of stages1519 Q.E.at peak Gain (B=0 T)5.0 x x 10 7 Gain (B= 1 T)1.8 x x x 10 5 Risetime (ns) TTS (ns)

27/6/05 Frascati31 Gain in B field (various orientations) B (T) G(T)/G(0) 2” 1.5”1” B(T) G(B)/G(B=0T ) PMT axis B   > critical angle

27/6/05 Frascati32 Pulse height resolution in B field 1” 2”

27/6/05 Frascati33 Rate effects (as a function of HV) rate capability is limited by maximum anode mean current (tipically 0.1mA for a 2” R5924 PMT) this is the ONLY relevant point, e.g. in B field if gain is lower by a factor F rate capability increases by 1/F with very high particle rates: try to reduce mean current HV increases

27/6/05 Frascati34 Rate effect as function of B field B field increases

27/6/05 Frascati35 Timing studies

27/6/05 Frascati36 Time resolution

27/6/05 Frascati37 Calibration of the HARP TOF Wall Intrinsic time resolution of scintillators =150 ps measured with laser system and in lab tests with cosmics Accurate equalization of time response of the different slabs is achieved with two methods Cosmic muons: Average values of equalization constants Calibration runs every 2-3 months, about one week Laser: Continuous monitoring of evolution of equalization constants Calibration runs twice a day, few minutes during interspill time M Bonesini – IEEE 2002

27/6/05 Frascati38 Calibration with cosmics before… …and after ~ 220ps A dedicated trigger setup is installed Time delays from reference trigger counter to the single slabs are equalized Time delays of slabs in central wall (ns) M Bonesini – IEEE 2002

27/6/05 Frascati39 The HARP Laser calibration system Laser Nd-YAG with passive Q-switch (dye), active/passive mode locking and 10 Hz repetition rate IR emission converted to a second harmonic ( =532 nm) by a KD*P SHG crystal Pulse: width 60 ps energy 6 mJ Beam splitter:  To ultra-fast (30 ps rise/fall) InGaAs MSM photodiode = START  To detector slabs through custom-made optical fibre system = STOP M Bonesini – IEEE 2002

27/6/05 Frascati40 Comparison of laser with cosmics calibration data  The two calibration methods provide similar accuracy on the equalization constants   The shifts of equalization constants (  ) measured with the two methods are well correlated (within 100ps) 70ps laser cosmics Shifts of calibration constants from 2001 to 2002 data taking M Bonesini – IEEE 2002

27/6/05 Frascati41 Estimate of costs TOF0 PMT assembly R4998 (1600 Euro x 40) 64K Euro scintillators 10K Euro Lightguides machining/supports/… i 5K Euro Electronics mountingsi/patch panels/dividers 5K Euro HV/signal cables 3K Euro 87K Euro TOF1 (or TOF2) PMT assembly 2” fine-mesh (2500 Euro x 35) 87.5KEuro scintillators 10K Euro Lightguides machining/supports/… 5K Euro Electronics mountingsi/patch panel/dividers 5K Euro HV/signal cables 3K Euro 110.5KEuro Sist Cal Laser Fast laser + fibers bundle 60K Euro laser diagnostics, electronics 5K Euro 65KEuro Sist Cal Cosmici scintillators, support, … 10K Euro Elettronica front-end QADC,TDC 40K Euro Discriminators 10K Euro NIM electronics 5K Euro Crate VME 8K Euro DAQ modules V1718 (2) 12K Eur 75KEuro HV supply 100 channels CAEN + mainframe 35K Euro Total 483 KEuro

27/6/05 Frascati42 Conclusions design for TOF stations well understood only some points to be defined connected with choice of size of TOF1/TOF2 PMTs (1.5” vs 2”) and divider for TOF0 PMTs (booster vs active divider) define electronics chain (TDC for high incoming rate): probable choice CAEN V1290 define the high-demanding calibration system (mainly laser based) test a prototype asap at LNF BTF, together with EMCAL