M. Bonesini

1
A possible design for MICE TOF stations

• M. Bonesini
• INFN Milano

2
Outline

• Introduction
• Considerations on environment
• TOF stations design
• Some simulation results
• PMTs tests
• Ideas for the calibration system
• Preliminary cost estimate
• Conclusions

3
Aim of TOF stations

• TOF0 experiment trigger
• TOF0/TOF1 PID on incoming muons
• TOF1/TOF2 PID on particle traversing the cooling
  channel
• Requirements
• Single detector resolution s60 ps
• High rate capability
• Sustain nearby 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
The environment
The beamline design puts harder and harder
requests on TOF stations

• Higher and higher particle rates ( now 2.3-2.8
  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 50-100 gauss),
  solenoids for TOF1/TOF2 (B.2 T)

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
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 100-200 g High rate 2.5 MHz.
• TOF1,2 environment
• High field 1-2 Kg Medium rate 0.5 MHz

9
Problems for high resolution scintillator based
TOF (?t lt 100 ps)

• ??pl dominated by geometrical dimensions
  ???(L/Npe)
• ?scint ? 50-60 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
• B field (shielding?)
• High incoming particle rates

10
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

Actual choice ??60 ps
Thin solution ??100 ps if all goes right
(perfect detector calibration, ...) I will retain
thick solution (1 slabs)
11
Some simulation studies TOF0
TRD Size 480x480
12
TOF0 X/Y singles projection
With 4 cm width slabs max counter rate seems lt
400-500 KHz. R4998 maybe OK with booster or
active divider circuit (studies under way)
13
Transit Time for Upstream Tof Planes

• Transit time between Tof0 and Tof1
• Quad fields are currently ignored
• Pions and muons can be distinguished

14
Downstream PID (from Rikard)
(No Ckov2)
good
15
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)
• L480 mm to avoid particles hitting lightguides
• W40 mm to reduce rate with a sensible counter
  number
• T1 to have good timing resolution

16
Mechanics for TOF0
View of X/Y plane 12 vertical counters , 12
horizontal counters
17
TOF0 support structure
18
Considerations for TOF0 PMT choice

1. Rate capability (up to some MHz)
2. Good timing properties (TTS)
3. Sustain magnetic field (we now assume lt50 gauss
   for TOF0)

19
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

20
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

21
Solenoid test magnet (B up to 50 gauss)
Test solenoid, PMT inside
Laser diode
Avtech pulser
22
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
23
R4998 PMT rate studies
24
Gain in magnetic field for R4998
Y
Z
50 gauss
x
25
Timimg properties of R4998 in B field
26
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
Considerations for TOF1/TOF2 PMT choice

1. Rate capability (up to some MHz)
2. Good timing properties (TTS)
3. Sustain magnetic field ( about 100-200 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).
28
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

29
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

30
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
31
Gain in B field (various orientations)
G(B)/G(B0T)
G(T)/G(0)
B
?
PMT axis
2
1.5
1
B (T)
? gt critical angle
B(T)
32
Pulse height resolution in B field
1
2
33
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
34
Rate effect as function of B field
B field increases
35
Timing studies
36
Time resolution
37
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
38
Calibration with cosmics
before
A dedicated trigger setup is installed
and after
220ps
Time delays from reference trigger counter to the
single slabs are equalized
Time delays of slabs in central wall (ns)
M Bonesini IEEE 2002
39
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
(l532 nm) by a KDP 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
40
Comparison of laser with cosmics calibration data

• The two calibration methods provide similar
  accuracy on the equalization constants d
• The shifts of equalization constants (Dd)
  measured with the two methods are well correlated
  (within 100ps)

Shifts of calibration constants from 2001 to 2002
data taking
70ps
cosmics
laser
M Bonesini IEEE 2002
41
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

42
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