A compact Silicon-Tungsten-Scintillator ECAL?

1
A compact Silicon-Tungsten-Scintillator ECAL?

• Graham W. Wilson
• Univ. of Kansas
• Cornell Workshop, July 13th 2003

2
Outline

• Introduction
• (Parametric Energy Flow Study -gt Tuesday)
• ECAL Design issues
• Simulation studies of
• i) Light collection uniformity in tile-fiber
• ii) EM energy resolution
• Strawman ECAL design
• Hardware activities

3
Big picture

• Electromagnetic calorimetry critical for
  separating photon-hadron separation in p-flow jet
  energy measurement
• ECAL cost likely to be a major issue
• Need to justify various options in terms of
  performance and cost
• Explore alternatives
• If B R2/RM is the FoM, a compact design (small
  RM) which we can afford to place at large B R2 is
  interesting

4
ECAL requirements

• Reasonable performance on single particle figures
  of merit
• Energy resolution ? 10/?E ? 1
• Angular resolution ? 1 mrad
• Hermetic measurement of missing energy very
  important.
• Contribute to excellent jet energy resolution.
  Aim for 30/ ?E.
• Essential to separate photons from interacting
  charged hadrons
• Higher B, higher R2, smaller Moliere radius
  (transverse size)
• So large volume, compact and dense
• Timing resolution.
• Bunch crossings potentially every 1.4 ns.
• Time resolution of 300 ps for photons helps
• Affordable.

5
Tungsten-Silicon ECAL

• Proposals exist for W-Si ECAL.
• The TESLA design, R1.7m, 40 layers of Silicon
  pads looks as if it can do the job (except maybe
  the timing), but is costed at 133 M (driven by
  3/cm2 Si cost)
• Eres 11/?E , Moliere radius 16.5 mm
• Our proposal centers on developing a cost
  optimized ECAL, with similar performance. This
  hybrid calorimeter would use Silicon sensors to
  do the fine pattern recognition and position
  measurement, plastic scintillators for fine
  sampling and timing.
• TILE-HCAL aim 10/tile ? 0.4 /cm2 (25 cm2area)
• 
  1.0 /cm2 (10 cm2area)

Sc-W-Sc-W-Si-W-Sc-W-Sc-W
6
Tile/fiber technique
Use blue scintillator. Embed wavelength shifting
fiber which absorbs blue scintillation light,
re-emits in the green. (Y11 absorption length
80 mm) Min. bending f 100 ? fiber f Several
fibers can be seen by one photo-detector
(CMS photo)
7
Recent developments
?

• Excellent light-yield for tile-fiber reported by
  CALICE TILE-HCAL (V Korbel, Jeju 02)
• 25 pe/mip with 5mm Scintillator, QE?15 PMT
• Higher QE devices (eg. APD) promise QE?75 and
  ease of use in B-field
• up to 20 pe/mip/mm looks possible
• Elegant and cheap on-tile optical readout
  possibilities Silicon PMs gt maybe 10/tile
  cost

Recent technique refinements suggest I) can
detect mips in each layer (if necessary) II)
scintillator sampling is much more likely to be
significantly cheaper than silicon sampling III)
A more compact ECAL with scintillator sampling
can be envisaged
8
Amsterdam workshop

• Discussions with Stan Bentvelsen (NIKHEF)
• Picked up a OPAL tile-endcap complete tile
  assembly
• Stan helped get us started looking at GEANT4
  simulation of tile response (he did similar
  GEANT3 studies for the OPAL design)

9
GEANT4 study of tile-fiber response
WIRED display of one photon rattling around in a
perfect tile.
with Eric Benavidez
Uses optical photon processes exampleN06.
Includes scintillation, Cerenkov radiation,
Rayleigh scattering, absorption, Fresnel
refraction, TI reflection.
Data runs saved with AIDA, analyzed in JAS3,
looking at light yield, uniformity, timing,
spectral characteristics.
Shopping list Real data !, validate
implementation (eg. Reflectivity,WLS properties).
Anyone tried something similar?
Study is making progress but results not yet
mature.
10
ECAL Design Studies

• This spring had looked at conceptual design
  issues of sampling frequency, sampling thickness
  and compactness in the framework of estimates
  based on parametrisations available in the
  literature expected to be good to around 10.
• Eg. Eres 2.7 ?tactive(mm)/fsamp (Wigmans
  p190) (labelled WPAR in next plots)
• Now using GEANT4 to repeat those studies and
  investigate actual hybrid geometries. GEANT4
  results sensitive to range cut.
• Despite EM showers are understood mantra, is
  there really good data in the literature which
  can be used to test/benchmark GEANT4 sampling
  ECAL results ?

11
ECAL Design Issues Sampling Frequency
WPAR
WPAR
Dense medium like Si has high sampling fraction
Issues cost of many layers of active
medium Cost of thin sheets of absorber.
12
ECAL Design Study Sampling Thickness
WPAR
WPAR
For thin scintillators, need enough
photo-electron statistics. (Kawagoe et al, 3.2pe
for 1mm scintillator)
1.5 pe/mip/mm looks like a sensible target for
thin tiles
13
Compactness
Upper curves, 1mm gap
TESLA TDR
Lower curves, no gap
Need to minimise gaps, reduce space needed for
fiber routing, by sharing fiber routing gaps
among layers
Assume 25 of scintillator thickness used for
readout
14
New studies
with Eric Benavidez (freshman)

• All calorimeter designs have 30 X0 of W (105 mm)
  to ensure adequate longitudinal containment and a
  fair comparison.
• GEANT4 studies are done primarily with 1 GeV
  photons (which are definitely longitudinally
  contained)

15
Scintillator-Tungsten Calorimeter
GEANT4 study based on TestEm3 example. 3 curves
correspond to range cuts of 100, 10, 1 mm (from
top to bottom)
1.4mm W plates (75 layers)
1 GeV photon
NB differs substantially from WPAR estimate
Sampling contribution only
16
Comparison (75 layers)
Focus just on the lowest line in both
GEANT4
WPAR
NB WPAR studies suggested E-res indep. of
thickness. Not with G4.
17
Range cuts

• 1 mm range cut is sufficient to estimate
  resolution with 2-3 accuracy. This corresponds
  to cutoffs of 1.6 and 8.9 keV for g and e in
  Tungsten
• However, the EM response still requires basically
  no cut (0.1 mm setting)
• (Sc/W 1.5mm/1.4mm), 1 GeV photon
• 100 mm 47.8 MeV, 11.6
• 10 mm 50.5 MeV, 10.7
• 1 mm 55.7 MeV, 10.4
• 0.1 mm 63.5 MeV, 10.2

18
E-resolution dependence on P.E. statistics
GEANT4 (1mm range cut)
1.4mm W plates
1.4mm W plates
Total sampling ? PE stats (2.5, 5, 10, 20
pe/mip/mm)

• PE stats contribution 2.5, 5.0, 10.0, 20.0
  pe/mip/mm

Sampling contribution
Lower curve sampling only
PE stats contribution 2.5, 5.0, 10.0, 20.0
pe/mip/mm
N.B. Suppressed zero
For 5 pe/mip/mm, at t1.5mm degrades from 10.5
to 10.9
19
Three strawman hybrid designs
Studied with GEANT4 (range cut 1 mm)
A super-layer (SL)
Sc-W-Sc-W-Si-W-Sc-W-Sc-W
HY75 (15 SL) HY135 (15 SL)
HY42 (14 SL)
In each case the Si layer is chosen as 400 mm Si
2.0 mm G10 as in SDMar01 detector
So far study uniform sampling structures.
20
HY75 HY135 HY42

• 1.4mm W plates
• 15 layers Si
• 60 layers of 1.5mm Scint.
• 4 layers ganged (30 pe/mip) ( if
  5pe/mip/mm)
• 15 super-layers each with mip-detection

• 0.778mm W plates
• 15 layers Si
• 120 layers of 1mm Sc
• 8 layers ganged (40 pe/mip)
• 15 super-layers

• 2.5 mm W plates
• 14 layers Si
• 28 layers of 2 mm Sc
• 2 layers ganged (20 pe/mip)
• 14 super-layers

E res 10.6/?E 7.9/?E
14.5/ ?E Moliere radius 19.3 mm
21.4 mm 16.5 mm
33 of the Silicon cost
(SDMar01 30X0 W 15.4/?E, 15.5 mm with 0.1 mm
range cut)
21
Complementarity - Correlations
HY135 7.9 E-resolution
Correlation improves resolution slightly
compensates for PE stats
Correlation coefficient -0.19
22
Linearity check

• Check HY75 with 50 GeV and 1 GeV
• Study done with 100 mm range cut (need to
  recheck)
• EM response consistent Scint. Fraction 3.78
  (50), 3.77 (1)
• Sc/Si response consistent 1.861 (50), 1.865 (1)
• E-res consistent 12.1/?E (50), 12.0/?E (1)
• Corr. Coeff. -0.14 (50), -0.13 (1)

23
Possible photo-detectors
Hamamatsu, multi-anode PMT, with 18mm?18mm
sensitive area. 16-channels has 16?4.5? 4.5mm (16
1mm ? fibers) 64-channels has 64 ? 2.25 ? 2.25
mm (4 1mm ? fibers)
Makes optical summing of several layers easy
B-field sensitivity and modest Q.E. probably
not the real detector solution.
24
Hardware plans

• Planning VME-based DAQ for cosmic and source
  tests, particularly for uniformity and light
  yield studies.
• Basics ordered including ADCs, discriminators
  and TDCs.
• Start getting experience with tile-fiber
  technique and various photo-detectors.

25
Potential Collaborators

• Kansas State E. von Toerne, T. Bolton
• Plan to collaborate
• Colorado Uriel et al
• Lots in common talking to each other
• Padova, INFN P. Checchia et al.
• Discussed in Amsterdam some commonalities
• CALICE JC Brient. Thin Sc/W/Sc elements
  conforming to alveolus structure can be
  accommodated in Si-W test beam
• US Si-W groups Oregon, SLAC
• TILE-HCAL groups DESY, Russia, NIU
• Japanese ECAL in contact with Kawagoe, Fujii,
  Takeshita

26
RD issues

• Calorimeter design optimization.
• No. of layers, R, absorber thickness, detector
  thickness, sampling frequency vs depth,
  transverse granularity of Si/Sc, tile shapes,
  groove patterns, gap sizes. Should Si-layer be
  independent of scintillator layers ? Fiber
  routing. Timing resolution.
• Studying with full shower simulation.
• Using optics simulation in tile-fiber design and
  testing studies.
• Demonstrating basic performance characteristics
• Light yield for thin scintillating tiles
• Response uniformity
• Scintillator/WLS/Photo-detector for timing
• Fiber routing for compact calorimeter
• Sound mechanical design
• Good quality thin absorber plates (sintering is
  cheap ..)
• Photo-detector characteristics

Getting started with lab test-stand with cosmic
rays and sources. Good for involving students.