WBS 4'3 PWO Monitoring Construction Project

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WBS 4.3 PWO Monitoring Construction Project

• Ren-yuan Zhu
• California Institute of Technology

2
Status of Construction Project

• Completed the monitoring test bench,
  determined the monitoring wavelength.
• 1st Laser installed and commissioned at
  CERN in August, 2001, and has been used in beam
  test. MO starts FY02.
• Construction of the 2nd and 3rd lasers and
  switches are on the way. The entire system is
  being integrated and will be installed at CERN in
  Summer, 2003. MO starts FY03.
• Study on mass produced PWO crystals were
  carried out for CMS ECAL.

3
People Involved in this Effort

• Liyuan Zhang 3/98 12/01, 8/02 now
• Kejun Zhu 7/99 10/01, 3/03 now
• Qing Wei 8/01 8/02
• John Hanson and Larry Mossbarger
• Duncan Liu of JPL
• David Bailleux at CERN Starting 8/01
• Adi Bornheim at CERN Starting Fall, 2002.

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Published Papers

• 8 papers in Nucl. Instr. and Meth. A486 (2002)
  102, A486 (2002) 196, A486 (2002) 89, A480 (2002)
  468, A469 (2001) 193, A438 (1999) 415, A413
  (1998) 297 and A376 (1996) 316.
• 5 papers in IEEE Trans. Nucl. Sci. NS-48 (2001)
  372, NS-47 (2000) 2102, NS-47 (2000) 1741. NS-45
  (1998) 686 and NS-44 (1997) 468.
• 10 CMS Notes 01-034, 01-008, 99-014, 99-069,
  98-083, 98-031, 98-007, 97-046, 95-157, 94-251.

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Why PWO Monitoring

• PWO radiation damage
• No damage in scintillation mechanism
• Damage is caused by radiation induced color
  center formation and is dose rate dependent.
• Variations of PWO crystal light output are
  monitored by measuring the variations of
  crystals transmittance.
• Monitoring light pulses are sent to crystals in
  the 3 us beam gap in every 89 us in situ at LHC.
• The design precision of CMS PWO ECAL is expected
  to be maintained by using the monitoring system.

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Monitoring Radiation Damage
Radiation induces color centers ? reduces
transmittance in the blue and green ?
monitoring the relative loss of
transmittance with pulsed laser light

• Little damage in the red
• monitor with red and IR
• laser pulse to separate
• out possible variations in
• the other components of
• the readout chain

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CMS ECAL Monitoring System
Initial calibration on test beam (as much
crystals as possible) In situ calibration with
physics ( W ? en, Z ? ee- ) using E/p allows
an inter-calibration of 0.5 in 35 days at low
luminosity. Monitoring evolution of crystal
response by light injection system
DATA LINK
DATA LINK
ADC OPTO
CTRL
OPTO
Laser and Switch Caltech responsibility Low
level distribution Saclay responsibility
FPPA or MGPA
SERIALIZER
APD
ADC ( x 12)
PWO
440 nm 495 nm 709 nm 796 nm
PN
FE
S
Laser
F1
F2
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Monitoring Wavelength Determination
d(T) versus d(LY)
Sensitivity and Linearity
440 nm was chosen for the best linearity
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Design of Laser Light Source
PC based Laser DAQ history recording of laser
performance.
2001
Optical switch directs monitoring laser pulses to
80 super-modules and from there to crystals
Two laser systems 440/495 nm and 709/796 nm
with own diagnostics on wavelength, pulse shape
and pulse intensity.
2003
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The 1st Laser System at Caltech
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YLF and TiSapphire Lasers
YLF Pump Laser
TiS Laser
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Laser Diagnostic Box
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Laser System Control
Control Two Lasers and Monitoring Run Mode
Laser Settings
Laser Waveform Display
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Laser Room at CERN H4 Test Beam
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1st Laser System Installed at CERN
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History Laser Pulse Energy r.m.s.

• Short term r.m.s 1.7, or 15 uJ.
• Peak to peak variation 15, corresponding to
  overall r.m.s. 3.7.
• Specification r.m.s. lt10.
• Drifting caused by power supply, temperature

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History Laser Pulse FWHM r.m.s

• Short term r.m.s 0.38 ns, or 1.6.
• Overall r.m.s. 0.5 ns, or 2.
• Specification FWHM lt 40 ns.
• Drifting roughly anti-correlated to the pulse
  energy.

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History Laser Pulse Timing Jitter

• Short term jitter 1.5 ns.
• Overall jitter 3.8 ns caused by the timing
  drifting.
• Drifting strongly anti-correlated to the pulse
  energy.

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Experiences in 2002 Beam Test
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PWO Resolution With Light Monitoring
Before and after beam irradiation with 10
variation of crystal light output
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A Red Laser added in Project 700 or 800 nm
gt 650 nm
650-710, 750-850 nm
PWO
Fiber
APD
lt 850 nm
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Decision on the Red Laser

• Specification
• Wavelength 650 to 700 nm or 750 to 850 nm
• Pulse Energy gt 80 uJ
• Pulse Width FWHM lt 50 ns
• Repetition Rate gt 80 Hz.
• 15 vendors were invited for quotation AdvR,
  Inc., Anderson Laser Inc., Evergreen Laser Corp.,
  Exitech, Lambda Physik, Melles Griot Laser Group,
  MWK Laser Products, OPOTEK, Photonics Industries,
  Physical Sciences Inc., Positive Light, Power
  Technology, Quantronix, Research Electro-Optics,
  Spectra-Physics.
• Quantronix chosen by ECAL TCG on 4/16/02.

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Laser Stability Lamp Degradation

• -20 in the 1st 1,000 h.
• Replace DC Kr lamp
• after 1,000 h.

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A Study on Temperature Effect
Room T Variations in 5 Days
TiS Pulse Energy and T
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Laser Temperature Dependence
TiS Pulse FWHM versus T

• No good correlation
• multiple factors
• ? 4/oC

good correlation ? 1.3 ns/oC
TiS Pulse Energy versus T
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Laser Stability Improvement

• A new laser barracks to accommodate three lasers
  and improve temperature stability
• Room temperature (21 /- 2)oC
• Dust free and humidity lt 60
• Minimum 60 cm free space on each side of the
  optical table.
• Laser pulse intensity may be stabilized by using
  a photo diode based feedback circuit which trims
  the power supply, so that the optical power is
  stabilized when lamp is aging. Quantronix is
  developing this kind of new power supplies as
  future product.

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New Laser Barracks
Three rooms, each housing one laser system,
allowing non-interrupted monitoring operation
even during laser service. Double door design
guarantees laser safety. Outer control room
contains all electronics for laser safety,
control and performance monitoring. Four air
conditioning units installed in each room provide
adequate environment for laser operation.
25/03/2003
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Safety
3 Class 4 Lasers
Laser Safety Box

• Interlocks 3 inner doors, 3 laser covers, level
  2 and calorimeter.
• Maintenance interlock bypassing inner door and
  laser cover, adding outer door.
• Emergency stop.

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The 2nd and 3rd Laser Systems

• The 2nd Quantronix (B/G) laser system was ordered
  in September, 2001, and was delivered to Caltech
  in May, 2002.
• The 3rd (IR/R) laser system was ordered in
  August, 2002, and was delivered to Caltech in
  March, 2003.
• Two laser systems are now being integrated
  together with diagnostics, 1 x 80 and 1 x 2
  switches and readout.
• The entire system will be delivered and installed
  at CERN in Summer, 2003, pending by the new laser
  barracks construction.

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TiSapphire Lasing Threshold
The 3rd IR/R Laser
The 1st 2nd B/G Lasers
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TiS Pulses of the 2nd and 3rd Lasers
440 nm
495 nm
796 nm
709 nm
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B/G TiS Pulse Energy r.m.s.
440 nm
495 nm
Stability 15 and 12 uJ for the B and G
respectively
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IR/R TiS Pulse Energy r.m.s.
796 nm
709 nm
Stability 13 and 4 uJ for the IR and R
respectively
34
B/G TiS Pulse FWHM r.m.s.
440 nm
495 nm
Stability 0.3 ns for both B and G
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IR/R TiS Pulse FWHM r.m.s.
796 nm
709 nm
Stability lt 0.2 and 0.2 ns for IR and R
respectively
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B/G TiS Pulse Center Jitter
495 nm
440 nm
Jitter is 2 3 ns for both B G
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IR/R TiS Pulse Center Jitter
796 nm
709 nm
Jitter is less than 1 ns for both IR and R
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Summary of WBS 4.3
After seven years RD and construction, the 1st
monitoring laser system has been successfully
installed and commissioned at CERN, and was used
in beam test. The 2nd and 3rd laser systems will
be installed at CERN in the Summer, 2003. The
entire US CMS WBS 4.3 monitoring construction
project is on schedule and cost. The MO starts
in FY03.
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Laser System MO Budget
Starting 2003, Quantronix contract to be paid
every May for the 2nd laser, every December for
the 1st laser, and every March for the 3rd laser.