M. Bonesini

1
MICE TOF stations construction planning

• M. Bonesini
• INFN Milano

2
Outline

• Introduction
• Present design for TOF0
• PMTs studies
• Current problems
• Funding timescale
• Present design for TOF1/TOF2
• PMTs studies
• Open questions (TOF0/TOF1/TOF2)
• Conclusions

3
Aims of TOF stations

• TOF0 experiment trigger
• TOF0/TOF1 PID on incoming muons
• TOF1/TOF2 PID on particle traversing the cooling
  channel
• TOF1/TOF2 contribute (t) to emittance
  measurement (st60 ps has been questioned by INFN
  referees for TOF2)
• Detector requirements
• Single detector resolution s60 ps
• High rate capability
• Sustain nearby not-uniform B fringe fields

4
TRD SEPT04 Layout
ISIS Beam
Iron Shield
TOF0
TOF1
Iron Shield
TOF2 Ckov2Cal
Diffuser
Proton Absorber
Ckov1
5
MICE
Cherenkov
Calorimeter
ToF0
Tof2
Tracking Spectrometers
Coupling Coils
Tof1
Beam Diffuser
Matching Coils
RFCavities
Liquid Hydrogen Absorbers
6
TOF0 design is presently based on SEP04 beamline
(mods may be foreseen for AUG05)

• Particle rates was around 2.4-2.8 MHz for TOF0,
  it seems that new beamline AUG05 will reduce it
  to 1.6 MHz -gt better if beam profile will not
  shrink in AUG05
• TOF0 in the fringe field of quadrupoles for TOF0
  B ltlt 50 gauss (mail from Kevin).

Conventional fast PMTs Hamamatsu R4998 with
booster or active dividermu-metal shielding
7
Summary of Rates (Sept04 from Tom Roberts)
Description LAHET Geant4 MARS
TOF0 2355 2693 2834
TOF1 462 529 557
Tracker1 422 482 507
Tracker2 284 324 342
TOF2 281 321 338
Good µ 277 316 333
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 before2 in. total thickness
of TOF0 and TOF1 ? 20 reduction in Good µ50
larger target acceptance ? 10 increase in TOF0
singles, 1 in Good µ.
8
Rates (Singles per ms) target insertion reduced
to get 600 good mu/sec (AUG05)
LAHET Geant4 MARS Average
TOF0 1722 1762 1508 1664
TOF1 813 832 712 786
Tracker1 771 790 675 745
Tracker2 629 644 551 608
TOF2 627 641 549 606
Good µ (Ev/sec) 621 635 544 600
9
Some simulation studies TOF0
TRD Size 480x480
SEPT04
10
TOF0 X/Y singles projection
SEP04 beamline (TRD) has fixed counter size to
L48 cm, W 4cm (T 1)
11
TOF0 AUG05 beamlinenews from 21/10/05 from T.
Roberts
Maybe (?) we may think to reduce detector size
L,W
We cannot go much lower for W PMT assembly
outer size is 3.2 cm, only realistic
possibility is L
We keep design as it is now for the present time
12
Scintillator counter layout

• based on present beamline assumptions for all
  TOF stations L480 mm, T1, W40 mm for TOF0,
  600 mm for TOF1/2. Choice between BC404/420
  scintillator or ELJEN Technology 230 (same
  quality)
• To be revised with AUG05 beamline design but
  soon, orders must be placed now for scintillator.
  Mainly I must fix L,W for TOF0

EJ230 BC420 BC404
Light output 64 64 68
lmax 391 nm 391 nm 408nm
Risetime 0.5 ns 0.5 ns 0.7 ns
Decay time 1.5 ns 1.5 ns 1.8 ns
Pukse FWHM 1.3 ns 1.3 ns 2.2 ns
Att length - 140 cm 140 cm
Seems a better choice
13
Mechanics for TOF0
View of X/Y plane 12 vertical counters , 12
horizontal counters
14
TOF0 support structure
No major changes foreseen up now
15
Considerations for TOF0 PMT choice

1. Rate capability (up to some MHz)
2. Good timing properties (TTS)
3. Sustain magnetic field (we now assume ltlt50 gauss
   for TOF0)

16
Conventional PMT test setup

• Laser source to simulate MIP signal (about 300
  p.e.)
• fast AVTECH pulser AVO-9A-C (risetime 200 ps,
  width 0.4-4 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,
  d20 cm, L50 cm) see later for details

17
Rate capabilities of PMTs

• To have a linear signal the mean average anode
  current (100 ?A for R4998 ) must not be exceeded
  -gt 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

18
Solenoid test magnet (B up to 50 gauss)
Test solenoid, PMT inside
Laser diode
Avtech pulser
19
R4998 PMT rate studies
20
Gain in magnetic field for R4998
50 Gauss
90 degs
0 degs
50 gauss
90 degs
21
Timimg properties of R4998 in B field
22
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
1 MHz
23
Timing resolution vs rate for R4998
Npe is estimated via absolute gain measure
(at SER peak)
24
Continuos pulsing vs ISIS-cycle

• Results for rate effects have been compared with
  a continuos pulsing rate R and simulating an
  ISIS-like cycle 1 ms at rate R 20 ms at no
  rate
• Results (as expected) show no difference

25
Final considerations for TOF0 PMTs choice

• tests are under way, but active divider seems a
  good option
• no problem for rate effects
• ESSENTIAL POINT to estimate for real final
  counters Npe (this determines rate behaviour) -gt
  counters prototypes available // cosmic testbench
  available

26
Back of the envelope calculation
Concerns
Intrinsic resolution
1) Light attenuation Timing degradation
with respect to distance from PMT. 2) Quality
of scintillator 3) Ageing effect
Needs evaluation with cosmics testbench
27
TOF0 planning

• Nov 05 decide L,W scintillator and place orders
  (EIJLEN vs BICRON) -gt needs final AUG05 rate maps
  at TOF0
• End 05 define choice between booster/active
  divider for R4998 (testscosmic testbench for
  Npe)-gt needs definitive B field maps at TOF0
• Parasitic testbeam with MEG friends at BTF asap
  -gt check TOF0 performances up to PMT output (st
  rate behaviour with e-)
• Mid 2006 combined testbeam with EMCAL at BTF -gt
  define electronic readout (V1290 ? TDCs)
• End 2006 define calibration scheme (cosmics
  laser)
• End 2006/beg 2007 buy FE electronics, laser
  calibr. system, HV
• Items 1-6 funded (120 KE) no funding yet for
  items 6
• But good news Sofia group is interested in TOF
  business, so we can be more confident on this
  schedule. We will define actual division of work
  later, according to interests. A Pavia group
  (still working on PMT tests) is planning to join
  TOF effort

28
TOF1/TOF2 design is still based on SEP04 beamline
design

• But timescale is less critical (as respect to
  TOF0)
• New point final B-field calculations after
  shielding of J. Cobb et al . Main result is that
  at PMT positions B//200 G, B__ 1000 G -gt
  fine-mesh PMTs need additional m-metal shielding

29
News from AUG05 from T. Roberts
Beam envelope seems smaller
Reduce TOF1/TOF2 size ?
30

• B at TOF for 7 configurations of Iron Discs
  Gap

• Calculations from J. Cobb, maybe some work can be
  done to shape shielding to change the relative
  weight of B//, B__

31
Considerations for TOF1/TOF2 PMT choice

1. Rate capability (up .5 MHz on full detector)
2. Good timing properties (TTS)
3. Sustain magnetic field ( about .1-.2 T for TOF2)

Tests at Lasa magnet test facility 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, S. Dussoni,
F.Gatti, R. Valle INFN Genova).
From MEG experiment
32
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

33
Used laser light source

• 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
34
Test magnet at LASA (B up to 1.2T)
PMT under test

• B field up to 1.2 T
• Free space 12 cm in height
• For other tests shielded conventional PMTs, we
  will refurbish the magnet, enlarging the gap up
  to 18-20 cm (field will go down to .4-.5 T)

35
Fine Mesh Photomultiplier Tubes

• Secondary electrons accelerated parallel to the
  B-field.
• Gain with no field 5 x 10 5 10 7
• With B1.0 Tesla 2 x 104 - 2.5 x 10 5
• Prompt risetime and good TTS
• Manufactured by Hamamatsu Photonics

R5505 R7761 R5924
Tube diameter 1 1.5 2
No. Of stages 15 19 19
Q.E.at peak .23 .23 .22
Gain (B0 T) 5.0 x 10 5 1.0 x 10 7 1.0 x 10 7
Gain (B 1 T) 1.8 x 10 4 1.5 x 10 5 2.0 x 10 5
Risetime (ns) 1.5 2.1 2.5
TTS (ns) 0.35 0.35 0.44
36
Gain in B field (various orientations)
G(B)/G(B0T)
G(T)/G(0)
B
?
PMT axis
2
? gt critical angle this points to mu-metal
shielding for TOF1/2
B(T)
37
Time resolution
38
Rate effects (as a function of HV)

• rate capability is limited by max 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

39
Rate effect as function of B field
40
Timing resolution vs rate

• Tests with MCA Ortec TRUMP 8K TAC Ortec 566 and
  CF discriminator
• ORTEC CF8000
• Timing resolution is not affected by rate R
• It depends as expected from Npe

41
Timing resolution vs rate
Conventional R4998 PMT with active divider
2 fine-mesh PMT
42
Rate effects

• Question any difference between rate capability
  in continuos pulse mode or in accelerator-like
  pulsed mode ?
• Answer no, as clear from the fact that rate
  capability is driven only by max Ia

bunched mode at rate R
Continuos mode at rate R
43
TOF1/TOF2 planning

• Not yet funded from INFN funds are up to now for
  TOF0 up to PMTs (no electronics, calibration
  system, HV). But design seems less challenging
  than TOF0 (similar, lower rates, even if with
  higher B field)
• We will do some RD/design work in parallel with
  TOF0, to avoid delays
• After funding, delivery may be end 2007/beginning
  2008 main bottlenecks (aside manpower) are
  delivery times for PMTS (4-5 months),
  scintillator (3-4 months)

44
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
• Laser cal syst Fast laser fibers bundle
  60K Euro
• laser
  diagnostics, electronics
  5K Euro
  
  
• 
  
  65KEuro
• Cosmics cal syst scintillators, support,
  10K Euro
• Front-end QADC,TDC
  40K
  Euro
• electronics Discriminators
  10K
  Euro

Got up to now 110KE ( 50KE in-kind material)
45
Main open points

• FE electronics (V1290 TDC with TOT corrections
  instead of V775 TDC V792 QADC) but this rate
  problem is common to all MICE detectors
• Fix beamline to define final geometry of
  scintillator counters, mainly L,W for TOF0 an
  early answer is needed by November 05
• Be completely sure of B field at TOF0 well below
  50 G
• Define by simulation the need of st 60 ps for
  TOF2
• Define by simulation is calibration is feasible
  with only through-going muons, exploiting
  detector redundancy (XY strips)
• and

46

• Remaining INFN funding
• Electronics, cal. System, HV for TOF0
• All TOF1/TOF2 (aside some modest RD for defining
  design)
• This mainly drives the TOF1/TOF2 timescale