Transcript Time of Flight System for the MICE Experiment

M. Bonesini
A possible
design for
MICEINFN
TOFMilano
stations
27/6/05 Frascati
1
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 Frascati
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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 s~60 ps
oHigh rate capability
oSustain nearby B fringe fields
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ISIS
Bea
m
TRD SEPT04 Layout
Iron
Shield
Proton
Absorber
TOF0
TOF1
Ckov1
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Diffuser
Iron
Shield
TOF2
Ckov
2Cal
4
…MICE
Tof2
Tracking
Spectrometers
Tof1
Coupling
Coils
Focus
Coils
Beam
Diffuser
Matching
Coils
Liquid
Hydrogen
Absorbers
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RF
Cavities
5
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)
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Summary of Rates (Sept04 from Tom Roberts)
Description
LAHET
Geant4
MARS
TOF0
TOF1
Tracker1
2355
462
422
2693
529
482
2834
557
507
Tracker2
TOF2
Good μ+
284
281
277
324
321
316
342
338
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 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+.
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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
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Problems for high resolution scintillator
based TOF (st < 100 ps)
•
spl dominated by geometrical dimensions (L/Npe)
•
sscint  50-60ps (mainly connected with produced
number of ’s fast and scintillator characteristics, such
as risetime) choice BC404
•
sPMT dominated by PMT TTS (160 ps for R4998)
st 
•
s
2
 s PMT  s pl 2
 s elec
N pe
2
scint
2
Additional problems in harsh environments:
1. B field (shielding?)
2. High incoming particle rates
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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: s100 ps if all goes right
(perfect detector calibration, ...) I will retain
thick solution (1” slabs)
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Actual choice : s60 ps
10
Some simulation studies: TOF0
TRD
Size
480x480
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TOF0 X/Y singles projection
With 4 cm width slabs max counter rate
seems < 400-500 KHz. R4998 maybe OK with booster
or active divider circuit (studies under way)
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Transit Time for Upstream Tof
Planes
•Transit time
between Tof0
and Tof1
•Quad fields are
currently
ignored
•Pions and
muons can be
distinguished
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Downstream PID (from Rikard)
(No Ckov2)
good
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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
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Mechanics for TOF0
View of X/Y plane: 12
vertical counters , 12
horizontal counters
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TOF0 support structure
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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)
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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, d~20 cm, L~50 cm) see later for details
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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
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Solenoid test magnet (B up to 50 gauss)
Test solenoid,
PMT inside
Laser diode
Avtech pulser
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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
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R4998 PMT rate studies
R4998 with modified
divider circuit: booster
for last dynodes
Structure
Stages
Gain
Rise Time
Transit Time
Transit Time
Jitter
Nominal: up to 1.5
MHz
27/6/05 Frascati
R 4998
Linear Focused
10
5.7  106
0.7 ns
10 ns
0.16 ns
R 5505
Fine Mesh
15
5  105 B=0
1.8  104 B=1 T
1.5 ns
5.6 ns
0.35 ns
23
Gain in
magnetic field
for R4998
Y
Z
50 gauss
x
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Timimg
properties
of R4998
in B field
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Rate effects studies for R4998
• done with available
R4998 with modified
divider from Hamamatsu
(booster on last
dynodes)
1 MHz
27/6/05 Frascati
• Light signal
corresponds to ~ 300
p.e.
26
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).
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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 Bfield, different inclination vs B field axis (),
diff laser rate to simulate incoming particle
rates
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Test magnet at LASA (B up to 1.2T)
PMT under test
27/6/05 Frascati
1.
B field up to 1.2 T
2.
Free space 12 cm
in height
29
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 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 (B=0 T)
5.0 x 10
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
5
1.0 x 10
7
1.0 x 10
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Gain in B field (various orientations)
G(B)/G(B=0T
)
G(T)/G(0)
B

PMT axis
2”
1.5”
1”
B (T)
 > critical angle
B(T)
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Pulse height resolution in B field
1”
2”
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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
HV
increases
• with very high particle
rates: try to reduce mean
current
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Rate effect as function of B field
B field
increases
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Timing studies
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Time resolution
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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
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M Bonesini – IEEE 2002 37
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)
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M Bonesini – IEEE 2002 38
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
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M Bonesini – IEEE 2002 39
Comparison of laser with cosmics
calibration data
 The two calibration
methods provide similar
accuracy on the
equalization constants d
Shifts of calibration constants
from 2001 to 2002 data taking
70ps
 The shifts of
equalization constants
(Dd) measured with the
two methods are well
correlated (within
100ps)
27/6/05 Frascati
laser
M Bonesini – IEEE 2002 40
Estimate of costs
TOF0
PMT assembly R4998 (1600 Euro x 40)
64K Euro
scintillators
Lightguides machining/supports/…
i
Electronics mountingsi/patch panels/dividers
HV/signal cables
10K Euro
5K Euro
5K Euro
3K Euro
87K Euro
TOF1 (or TOF2)
PMT assembly 2” fine-mesh (2500 Euro x 35)
scintillators
Lightguides machining/supports/…
Electronics mountingsi/patch panel/dividers
HV/signal cables
Sist Cal Laser
Fast laser + fibers bundle
laser diagnostics, electronics
Sist Cal Cosmici
Elettronica
front-end
HV supply
scintillators, support, …
87.5KEuro
10K Euro
5K
Euro
5K Euro
3K
Euro
110.5KEuro
60K Euro
5K Euro
65KEuro
10K Euro
QADC,TDC
40K Euro
Discriminators
NIM electronics
Crate VME
DAQ modules V1718 (2)
10K Euro
5K Euro
8K Euro
12K Eur
75KEuro
100 channels CAEN + mainframe
35K Euro
27/6/05 Frascati
Total 483 KEuro
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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
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