Quartz Plates As Detectors

1
Quartz Plates As Detectors

• Future HEP Calorimeters will have to deal with
  very high radiation as a result of increased
  collider luminosities.
• As an example a very high radiation dose on HE
  scintillators over a period of 10 years of LHC
  operation is expected to damage the detector
  beyond usefulness.
• We wanted to understand if we could replace
  scintillators with Quartz Plates and used
  Cerenkov radiation as a detector method.
• We use GEANT4 to study the performance and the
  properties of such a detector.
• And have performed some preliminary test beam
  experiments at Fermi National Lab in Chicago, IL.

2
Calorimetry

• In HEP calorimeters measure the energy of
  particles by stopping the particles and providing
  a signal that is proportional to the energy
  deposited in the calorimeter.
• There are two parts of a calorimeter.
• The absorber which stops the particle.
• The detector which produces the signal.
• Many early calorimeters were made with one
  material serving as both absorber and detector.
  Now homogeneous calorimeters are normally only
  used to detect electrons and photons which can be
  stopped over a short distance even at high
  energies.
• Hadronic particles (pions mostly) are typically
  detected in sampling calorimeters which have a
  high density absorber layer (like iron) and a
  detecting layer. These typically have worse
  resolution because most of the energy is
  deposited in the absorber, but also are much
  cheaper which is a significant concern because
  you often need several meters of absorber to
  fully contain the particle shower.

3
Cerenkov Radiation Calorimetry

• Almost any Physics process that creates light can
  be used as a detection method.
• Scintillating materials are one of the most
  popular choices because they produce plenty of
  light making even low energy detection easy.
• Scintillators can darken when exposed to high
  radiation doses.

• Another process that can be used is Cerenkov
  Radiation.
• Whenever a particles speed (bc) exceeds the
  speed of light in the material (c/n) it is
  traversing it emits a coherent wavefront which is
  called the Cerenkov effect.
• While the Cerenkov effect doesnt typically
  produce as much light as scintillators, it does
  occur within many materials including those that
  can withstand high radiation doses.

Particle emitting Cerenkov radiation through a
material.
4
Geant 4 Simulation

• We used Geant 4 to perform Monte Carlo
  simulations of a Prototype Quartz Plate Cerenkov
  Calorimeter.
• The prototype consists of twenty 5mm thick quartz
  plates each separated by 7cm of iron absorber.
  The absorber and quartz layers are both 20cm by
  20cm square. The quartz plates each have nine
  optical fibers placed in them 5 on one side and 4
  on the other.
• Longitudinal and transverse shower profiles were
  simulated.
• The Longitudinal simulations were done for
  electrons, pions, and photons at energies ranging
  from 10GeV 120GeV.
• Transverse profiles were done for 120 and 80 GeV
  protons.

5
One Simulated Layer
6
Four Simulated Layers
7
Proton Longitudinal Shower Profile
8
Pion Longitudinal Shower Profile
9
Electron Longitudinal Shower Profile
10
Transverse Energy Profile 120 GeV
11
Test Beam at Fermilab

• On the week of February 12-18th 2006 we conducted
  a test beam experiment with part of our
  prototype.
• We only had three quartz and supplemented them
  with three UVT plates (Plexiglas plates with UV
  extended optical range), for a total of six
  layers.
• By varying the amount of iron in front of or
  between the plates we were able to obtain data
  for a range of depths.
• We obtained data for beams of 120 GeV and 66GeV
  pions.
• The resulting data is compared to a Geant 4
  simulated photon count at each PMT.

12
Assembly of the Quartz Layers
Quartz Plate with Fibers inserted
Placement of wrapped Quartz Plate in Frame
Wrapped Quartz Plate
13
Calorimeter Prototype at Fermilab
Close up view of calorimeter.
Looking down the beam line with extra iron placed
in front of Calorimeter.
14
Simulated PMT Response Test Beam Data
15
Future Work

• We have test beam scheduled at CERN from June
  28th to July 5th.
• We will have a full 20 layer calorimeter
  prototype and also have scintillating plates for
  comparison purposes.
• Several beam energies will be run allowing us to
  compare data to the full range of our
  simulations.
• Future simulations need to be done as well.
• While the transverse energy graphs look good we
  need to look at simulated transverse PMT
  response, to make sure we arent loosing to much
  signal. This is currently being done.
• Also the current simulations need to be refined
  and better understood. This is also currently
  being worked on.
• The current simulation uses fiber which is not
  what will be used in the final prototype so this
  must be changed and the effect of that change
  modeled.