MICE Berkeley, Oct 2002 MICE Spectrometer Design Proposed Tracker Implementations A. Bross Fermilab.

MICEBerkeley, Oct 2002

MICE Spectrometer Design

Proposed Tracker ImplementationsA. BrossFermilab


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



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



6 D measurement t 2 ns E/E 10%

Approximately 3000 muons needed for 10 measurement


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.


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


Fiber Tracker Channel

MirrorScintillating

Fiber

Optical connector

Waveguide

VLPC cassette

Electronics

Cryostat


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


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


VLPC Readout Option

VLPC (Visible Light Photon Counter)

Cryogenic APD operating @ 9K

Characterization/test/sort Cassette Assignment

As shown


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’


Lab 3 CRT (Singlet) Light Yield

Lab 3 CRT Light Yield Summary Covers Waveguide lengths 7.7-11.4m


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


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


Gaseous Electron Multiplier TPC


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


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


TPG Electronics

HARP electronics can be used for MICE TPGs


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


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


Radiation Backgrounds

Snap-shot of background measurements. We are on a VERY steep (and slippery) slope!


Radiation Backgrounds

Question regarding equilibrium point e/ Emax = 10 MeV e brem Compton e


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!


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


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.

MICE Berkeley, Oct 2002 MICE Spectrometer Design Proposed Tracker Implementations A. Bross Fermilab.

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