CLAS12 Preshower

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CLAS12 Pre-shower
Summery of the TWG meeting
S. Stepanyan (JLAB) Collaborating
institutions YerPhI, JMU, OU, NSU, WM,
Orsay-IPN, JLAB
CLAS12 Detector workshop, February 21, 2008 , JLAB
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CLAS12 EC/PCAL TWG

• 830- PCAL design status (Dave Kashy)
• 845-Status of the PCAL prototype and future
  plans (Mikhail Yurov)
• 915-RD projects Plans for testing of different
  types of glues and PMTs (Kevin Giovanetti)
• 930-RD projects Procedures for scintillator
  cutting, fiber gluing and QC (Jose Riso)
• 1015 - PCAL construction phases and schedule
  (Stepan Stepanyan)
• 1030 -PCAL simulations and reconstruction issues
  (Stepan Stepanyan)
• trigger, reconstruction and calibration
  procedures with fADC
• from GSIM12/RECISIS12 to GEANT-4/C
• 1045- Plans for EC upgrade (Cole Smith)
• Talks are on the web CLAS12 wiki

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CLAS12 PCAL project WBS 1.4.2.2.2.3
CLAS12 detector

• Proposed configuration for the pre-shower
• lead and scintillator sandwich with three stereo
  readout views, UVW (5 layers per readout view)
• fine segmentation of scintillator layers in the
  forward region for all three UVW views
• light transport from scintillator to PMT via
  green wave-shifting fibers embedded in grooves on
  the surface of the scintillator strips

Pre-shower calorimeter
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PCALEC simulations (15 layers and 108 strips)
Electromagnetic shower reconstruction at high
energies

• Energy resolution for electrons thrown in the
  center of the of the calorimeter

Efficiency of two photon reconstruction from high
energy p0gg decays
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Outcome of RD efforts
Design parameters of the pre-shower are
established 15 layers of the lead and
scintillator, 2.2mm lead, 10mm scintillator 4.5
cm segmentation of the scintillator layers in
forward region

• Choice for the scintillator, WLS fiber, and PMT
• Fermi Lab extruded scintillators, 4.5x1 cm2 with
  3 grooves
• Kuraray, 1mm diameter Y11 single clad
• HAMAMATSU R6095 selected with Q.E.gt16 _at_ 500 nm

Expected photo-electron yield 11p.e./MeV for 3
fibers (yield for EC readout from the test
measurements was 8.4p.e./MeV)
Final price tag for the construction of 6 modules
of PCAL is set
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Design Status (D. Kashy)
Most of critical details are worked out!

• Window design and analysis complete
• Partial Full Scale prototype being fabricated for
  testing
• PMT Housing Design complete and Prototypes built
  and used in a complete PCAL prototype
• Cosmic tests complete
• Testing during g12b
• Overall Box Size growing to give larger
  acceptance and allowed by move of W readout to
  back.
• CAD model for box nearly complete.
• Design for support of guts nearly complete
• Headers for PMT mounting and fiber routing
  designed

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3d CAD Model
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Window Prototype Model

• Calculated Deflection under max load 3.8mm(0.15
  inch)

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Support Arms
Outer
Nose
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What is left to do

• Final approval of moving of W-readout to the
  V-side (back of the PCAL) simulations are
  needed
• Final arrangement of readout segmentation for
  each U-V-W views simulations are needed
• Final modifications from size increase
• Analysis of supports
• Work out details of FTOF attachment to PCAL
• Detail drawings of all parts and assemblies

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PCAL design issues

• PMTs along sides of modules from adjacent sectors
  are very close to each other. On the top of
  modules, where the distance is largest, the gap
  is only 15mm wide.

• This will lead to
• Difficulties during the installation - requires
  positioning of individual modules with better
  than few mm accuracy
• Could result in damaging of fiber enclosures, if
  measured dimensions on forward carriage will
  change due to the load change
• Makes maintenance of modules (replacing PMTs)
  very hard, some spots may become inaccessible

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PCAL design issues (cont.)

• Current design assumes equal number of PMTs for
  each U, V, and W-views (64 PMTs per view, total
  of 192 PMTs per module). This requires double
  tower readout with single PMT at large angles.
• Having U-view with finer segmentation
  farther to large angles might be beneficial for
  overall detector performance. Simulations are
  needed to test different configurations of the
  readout segmentation.

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PCAL prototype (M. Yurov)
Prototype Side View

• Prototype components
• Fermi Lab scintilliator strip 45X10mm,
• 3 grooves
• WSF (KURARAY 1mm, SC)
• Lead 2.2mm
• Aluminum frame and support structure

Prototype Top View
X1
X2

• 15 PMTs 5(strips) 3(planes) 1(stack)
• 15 fibers 3(fibers) 1(strip) 5(layers)
• 75 scintillator strips, 225 fibers and 15 lead
  plates

Y
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Test setup
Coincidence between counter signal and any of
five X1-plane signals forms the trigger.
Counter consist of scintillator plate (2022cm),
conventional lightgide and PMT.
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• To calibrate the prototype response to energy
  deposition of Minimum Ionizing Particles (MIPs)
  has been studied.
• For each PMT, a MIPs peak position, at given HV,
  was determined using two Gaussian fit to the ADC
  distribution.

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Single photoelectron peak for PMTs

• Readout electronics consisted of the LeCroy 1881
  ADC and discriminator.
• As a gate for ADC, discriminated pulse from the
  trigger PMT was used.
• Signals of the test and the trigger PMTs were
  delayed and connected to the ADC inputs.
• The ADC information was read out using the
  standard CLAS DAQ software.
• LED's signal frequency, amplitude, width etc. are
  managed by signal function generator.

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SPE determination

• Since the position of SPHE peak at nominal HV
  was too close to pedestal it was decided to
  perform another sets of measurements to minimize
  uncertainties due to bad fit values.
• With LED amplitude attributed to SPHE spectra 4
  measurements with different HV settings have been
  done.
• In order to check gain curve behavior another 4
  measurements have been done with the same HV
  setting but black paper was removed from test PMT.

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Measurements

• To determine position of SPHE peak position the
  ratio

has been plotted as a function of HV and
fitted. Aopen - mean of ADC distribution for
opened PMT above pedestal Aclose - mean of SPHE
peak above pedestal Tr(HVi) mean of ADC spectra
for i-th HV setting Tr(HV1) mean of ADC spectra
for nominal HV setting
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Measurements

• The absolute light yield was determined with
  respect to results of MIP energy deposition
• Mean of the MIP spectra corresponds to 10 MeV
  energy deposition
• Splitter used in cosmic test splits PMT signal as
  12

• For this particular PMT
• MIP position in ADC channels above pedestal 102.9
• Single photoelectron peak position in ADC
  channels above pedestal 3.8
• Number of photoelectrons per 1 MeV energy
  deposition 8.2

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Summary of the results
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Activities at JMU (K. Giovanetty)

• Test of different optical glues this summer
• Test setup for PMT gain measurements
• Development of a model for light collection
• Maintenance of the PCAL wiki page

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PCAL Construction (S. Stepanyan)

• Construction of the PCAL consists of several
  quasi-independent processes
• processing of scintillators and gluing of fibers
  (WM)
• assembly of PMTs and dividers (JMU)
• stacking of scintillator-lead layers (JLAB)
• mounting PMTs and testing (JLAB)
• storage of ready modules before moving to the
  Hall B (JLAB)
• Each process requires independent man power and
  work space
• Most of these processes require clean
  environment, climate controlled areas
• Few details of construction must be worked out
  before construction starts
• type of glue to use
• gluing procedure and QC
• fiber channeling during the stacking
• polishing of fiber ends on after assemble
• PMT dividers active vs. passive

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Construction time line and manpower
If MRI is approved and money for procurement will
be available, we will need some 12 GeV JLAB money
in FY09 to start construction
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Issues and questions to be addressed

• For PCAL construction
• type of glue to use
• gluing procedure and QC
• fiber channeling during the stacking
• polishing of fiber ends after assembly
• PMT dividers active vs. passive

• Software issues for PCAL and EC
• trigger with fADC and FPGA
• reconstruction and calibration with fADC pulse
  width and energy resolution

• For EC
• repair of hard to reach channels
• PMT signal splits TriggerADC/TDC - delay cables

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Plans for RD in FY08

• Must -
• Continue testing of different optical glues -
  will require about 1000 to purchase glues, work
  will be done at JMU
• Testing  of different voltage dividers for PMTs -
  will require about 2000 for a design and
  assembly of the dividers, work will be done at
  JLAB?
• Continue testing new scintillators from FNAL -
  will require about 2000 to order fibers. Work
  will be done at JLAB
• Develop scintillator cutting technology will
  require test samples. Work will be done at
  JLAB/WM
• Develop procedures for gluing tightly connected
  with (1). Work will be done at JLAB/WM, will
  require 3000 for fibers and glue
• Continue tests of the small prototype (on beam) -
  Work will be done at JLAB
• Overall the estimate 8000 for purchases and
  money for a visitor for 6 months.
• Should
• Continue die development with FNAL, requires
  about 10000
• Disassemble and reassemble the small prototype
  with new (latest) FNAL scintillators. Work will
  be done at JLAB. Will require some machine shop
  time, stock room items, electronic lab time,
  etc., about 1000

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Summary

• Pre-shower RD and PED are in progress
• Main design parameters are established using the
  full GEANT simulations, but there are still few
  issues to resolve before the design is completed
• Key components of the PCAL (scintillator-fiber-PMT
  ) are selected, but there are few details to be
  worked out for construction
• Cost estimate for the whole project is completed
• Contingency and risk analysis are performed
• Stages and required resources for construction of
  the main detector are identified
• MRI proposal for amount of 780K (630K) is
  submitted to NSF total of 60 of whole PCAL
  procurement if approved construction will start
  in FY09

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Surface mount vs. through hole mount
3 grooves with 1 mm diameter single clad Y11, 4.5
cm wide scintillator
1 through hole with 1.5 mm diameter single clad
Y11, 4 cm wide scintillator
Fibers were glued with BC600 optical cement
A la Minos
Minarva strip
Test Setup
Gate
Trigger PMT-T
ADC
Test PMT
Trigger PMT-D
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Test PMT ADC distributions
3-fibers, 1 mm in diameter
1 fiber, 1.5 mm in diameter
Pedestal is at 341
Single photoelectron peak of test PMT
4 cm wide scintillator with 1 through hole for a
single 1.5 mm diameter fiber

• has 25 less light per unit of width than
  current PCAL design
• 1.5 mm diameter fibers are 2.5 times more
  expensive than 1mm fibers
• will require 10 more readout channels
• broken fiber will have much bigger effect
• may be easy to assemble

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PMT and Housing