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MICEBerkeley, Oct 2002
MICE Spectrometer Design
Proposed Tracker ImplementationsA. BrossFermilab
MICEBerkeley, Oct 2002
Spectrometer Requirements
Experimental goal is Measure 6D emittance
n = D (x,y,t) and (x’,y’,t’) (px/pz,py/pz,E/pz)
Single-particle experiment Measures xi,yi position at zi
Plus possibly t Resolution requirement
rms 10% of beam parameter rms At least 3 planes 1 m long (2/3 turn @ 200 MeV/c and
3T Beam with 30 MeV/c p
MICEBerkeley, Oct 2002
Spectrometer Requirements
Rough transverse beam specs
x,y = 5 cm x’,y’ = 100 mrad
Using the PSI LOI analysis SCIFI option
4 planes 150 micron resolution
On the order of 1000 muons needed for 10
Assumes contamination < 10% rejection 99% e identification
Does not address problem of operating near RF cavities
Ionizing background (e,) EM (rf) background
Transverse cooling for 7, 14,and 28 MeV cooling channels
MICEBerkeley, Oct 2002
Spectrometer Requirements
6 D measurement t 2 ns E/E 10%
Approximately 3000 muons needed for 10 measurement
MICEBerkeley, Oct 2002
Detector Options
Two Options are currently under study for trackers
Scintillating Fiber Based on D0 experience Uses 350 micron diameter fiber Visible Light Photon Detector Readout 45,000 channels (in most aggressive configuration)!
GEM based Time Projection Chamber or TPG Based on HARP design
– Plan to use HARP electronics But will use Gaseous-Electron-Multipliers (GEMs)
instead of wires for gain region.
MICEBerkeley, Oct 2002
Fiber Tracker Option for MICE
Fiber Tracker Baseline Design Assume
Backgrounds are extremely high! Requires use of smallest fiber diameter possible
– 350 micron u-v-t readout station
Doublet structure 0.3 % Xo per station
5 stations/spectrometer This yields a system with about 45k channels!
VLPC readout <3 m light piping fibers from detector to VLPC
MICEBerkeley, Oct 2002
Fiber Tracker Channel
MirrorScintillating
Fiber
Optical connector
Waveguide
VLPC cassette
Electronics
Cryostat
MICEBerkeley, Oct 2002
Fiber Tracker Parameters
Mechanical 300 mm active diameter 5 stations in 1 m path Material budget 0.8g/cm2
Electrical/Readout 45,000 channels VLPC readout (1 mm pixel)
Tracking Expect 8 pe signal/singlet x = y 40 m p0.2 MeV/c
Timing 20 ns integration time
2 ns time-stamp resolution
+1
MICEBerkeley, Oct 2002
Scintillating Fiber Ribbons
Interlocking doublet 835 m 3HF scintillating fiber
Fluorescence 525 nm (peak) to 610 nm
Grooved substrate - machined Delrin
Pitch between 915 and 990 m Optimal P/d 1.2
Substrate put into curved backbone Fibers glued together with
polyurethane adhesive Ribbons is then QC’ed using
scanning X-ray source Technique is very fast
All MICE planes require 4 MMeffort + Tooling
MICEBerkeley, Oct 2002
VLPC Readout Option
VLPC (Visible Light Photon Counter)
Cryogenic APD operating @ 9K
Characterization/test/sort Cassette Assignment
As shown
MICEBerkeley, Oct 2002
1024 Channel VLPC Cassettes
Engineering Design 8 – 128 channel modules Cassette carries two 512 ch
readout boards Front-end amp/discriminator Analog – SVX IIe
3’
MICEBerkeley, Oct 2002
Lab 3 CRT (Singlet) Light Yield
Lab 3 CRT Light Yield Summary Covers Waveguide lengths 7.7-11.4m
MICEBerkeley, Oct 2002
MICE Fiber Tracker
Conventional FT using MAPMT
With same length of readout fiber
If waveguides are used 430 nm = 1300 dB/km (1/e =
3.4m) 525nm = 450 dB/km (1/e =
9.6m)– D0 measured 8.1m @ f
p = 525 nm
QE = 20% Yield =
9 X 20/80 X exp(-5/3.4)/exp(-5/8)
1 pe Waveguide length would have to
be limited to 2 to 3 meters
Attenuation vs. wavelengthof Kuraray clear fiber
3 HF
Conventional Blue
MICEBerkeley, Oct 2002
TPG Concept for MICE
Basic TPG Design 90% He – 10% iso-
butane TPC with gain section consisting of 3 GEMs
Readout plane - strip geometry
5 m Cu on 50 mKapton. 70 m holes with 140 m pitch
MICEBerkeley, Oct 2002
Gaseous Electron Multiplier TPC
MICEBerkeley, Oct 2002
TPG Parameters
Mechanical Active diameter = 300 mm Active length = 1000 mm Material budget
0.01g/cm2
Drift 500 V/cm (50KV) 1.7 cm/s
Electrical/Readout 3 GEM amplification
Gain upwards of 104-105
Gated during RF pulse – [TPG readout between pulses]– 60 s max drift time– 500 s exposure time
u,v,t hexagonal pads Readout with u,v,t strips
– 450 m pitch 120 samples in z
MICEBerkeley, Oct 2002
Expected TPG Performance
Tracking x = y 150 m p 0.2 MeV/c With u,v,t readout expect to be able to readout
400 muons during a single time window
Timing 60 s readout time The TPG requires a fine grained hodoscope in order
to “tag” each muon so that its arrival time relative to the RF phase can be measured.
Possibly SCIFI layer + High resolution (50-100 ps) TOF
MICEBerkeley, Oct 2002
TPG Electronics
HARP electronics can be used for MICE TPGs
MICEBerkeley, Oct 2002
HARP TPC Electronics
Based on ALICE prototypes ALTRO (Alice Tpc ReadOut)
chip Sophisticated zero-suppression
and time-over-threshold logic 100 s depth @10 MHz sampling
Uses FEDC board version of ALTRO readout system
1 FEDC = 48 channels 4 - 10 bit ADCs + ALTRO on
daughter card (12/FEDC) Fed by preamps on TPC pad plane
4000 channels available 6 9U VME crates MICE TPG 600X3X2 = 3600 ch
Can handle expected data rates
MICEBerkeley, Oct 2002
MICE Tracking Decision
In the absence of ionizing (e + ) and electromagnetic radiation backgrounds from the cavities, and safety considerations because of the LH absorbers, both trackers can easily work.
Final decision will depend on Actual background radiation environment
Includes EM interference concerns for TPG– To be tested at CERN in the near future
Tracking performance of each option in the expected rad field
– Big uncertainties (or large extrapolation) until prototype 201 MHz cavity under test
Safety issues Need to be studied for TPG option Not an issue for fibers since detector passive
And eventually – COST Fiber tracker is dominated by channel count (VLPCs) TPG saves a great deal by reusing HARP electronics
MICEBerkeley, Oct 2002
Radiation Backgrounds
Snap-shot of background measurements. We are on a VERY steep (and slippery) slope!
MICEBerkeley, Oct 2002
Radiation Backgrounds
Question regarding equilibrium point e/ Emax = 10 MeV e brem Compton e
MICEBerkeley, Oct 2002
Strawman Background Hit comparison
Based on 1 MHz hit rate from 30 cm long, 835 mm diameter fiber located about 1.5 m from pill-box cavity in Lab G at Fermilab (B=2 T, 10 MV/m) [Assume from x-rays only – not correct]
This corresponds to an x-ray fluence of 6X107/cm2-s Assumes x-ray energy 50 keV
Hits/read Fiber Tracker
– 6X107 X 20X10-9 X[1-exp(-0.2cm2/g X .8g/cm2)]X707 125 TPG
– 6X107 X 60X10-6 X[1-exp(-0.17cm2/g X .01g/cm2)]X707 4300
But TPG has 120/5 more “measurement stations” Fiber Tracker also has possibility of 2 ns time-stamp In both systems an x-ray interaction may produce more than
one hit Low energy x-rays (<10 keV) more of a problem for TPG than
fiber tracker where they do not register a hit. Need Measurements with Final Cavity to be sure!
MICEBerkeley, Oct 2002
Conclusions
In the absence of backgrounds, the choice of tracker for the spectrometers would likely only be based on cost and safety considerations.
Both TPG and SCIFI can easily meet the experiment requirements in terms of tracking performance (resolution) and pattern recognition (in zero BG conditions) and do so within an acceptable material budget
Radiation, ionizing + from RF cavities still present a very difficult environment in which to operate, however
Sensitive electronics (front-end preamps) may also have problems due to EM leakage from cavities
Detailed shielding question Constraints imposed by safety requirements will be
severe for any active components within the 5 m safety-zone
MICEBerkeley, Oct 2002
Conclusions
Critical tasks “Best-possible” measurement of ionization background
Preferably with 201 MHz cavity Demonstration of prototype operation near cavity to
determine effect of EM fields on sensitive front-end electronics for TPG
Conformation of light yield measurement for Fiber Tracker
Complete analysis of safety risks and constraints that will be imposed on the detectors
Operation of prototypes near RF cavity Again 201 MHz cavity best
It is clear that getting the first 201 MHz cavity built is of critical importance to both MuCool and MICE.