Laser%20Systems%20and%20Instrumentation

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Laser Systems and Instrumentation

• D. McCormick, J. Frisch, T. Kotseroglou,
• M. Ross, D. Schultz

Josef Frisch
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NLC Laser systemsKey technical requirements

• Laser Wire Lasers Beam profile measurement.
• High peak power gt10MW
• Clean TEM00 Mode output required
• Large number of systems 40 lasers, 200
  Interaction points.
• Some single bunch systems, some multi-bunch
• Polarized Source Lasers Drive polarized
  photocathodes
• Require control of wavelength, pulse shape
• Require exceptional (lt0.5 RMS) intensity control

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Source Laser Requirements
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Source Laser Technical Choices Baseline Design.

• Use conventional materials
• Titanium Sapphire for main laser.
• Flash lamp pumped Neodymium YAG for pump laser.
• Pulse shaping
• Use dispersive pulse shaping to avoid exotic
  electronics.
• Intensity stability control
• Use long pump pulse / feedback for intensity
  stabilization.
• This is the most difficult requirement exceeds
  state of the art for lasers of this complexity.
• Reliability
• Use dual laser systems with automatic switch over

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Source Laser Baseline Design Block Diagram
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NLC Source Laser Technical Risks

• Intensity stability requirement exceeds state of
  the art
• System reliability must be exceptionally high for
  a complex laser.
• System uses flash lamps, requiring significant
  maintenance.

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Source Laser Technical Challenge Complexity
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Other Source Laser System Components

• Polarization, Intensity, Steering, Spot size
  control.
• Requirements similar to SLAC,
• not expected to be a technical problem.
• Beam transport line
• Use conventional vacuum hardware, minimal
  technical risk
• Photocathode
• The performance of the photocathode directly
  influences the source laser requirements.
• Photocathode RD will reduce laser uncertainties

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Source Laser Cost Model

• Use Baseline Design
• Bottoms up costing
• Use commercial parts where possible
• EDI and Labor costs based on engineering
  judgement from SLAC experience with laser
  development
• Items included
• 2 Source lasers at gun, 1 at test lab, 1 spare
• Clean rooms required for operating lasers
• 1 Prototype laser required.
• RD required to reduce cost and risk
• Source laser costs 4-10 Million (breakdown
  dependant)

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Laser Wire Requirements
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Laser Wire Baseline System Technical Choices -
Single bunch system

• Use commercial Q-switched Neodymium YAG laser
• Provides gt30MW at 350nm wavelength (sufficient)
• Good transverse mode quality
• Technical issues
• System is long pulse (4 nanosecond), high energy
  (gt100mJ). Optical damage is a concern
• System uses flash lamps, maintenance required.
• Relatively high cost.

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Laser Wire Technical Choices Multi-bunch system

• Use a variant of the NLC source laser, with
  recompression and frequency doubling
• System has very similar requirements
• Most technical risk already assumed in the source
  laser.
• Potential for time resolved measurements of
  electron bunches.
• Exceptional timing stability required for this
• Technical Issues
• Complexity more severe than for source due to
  the larger number of lasers
• Maintenance requirements high due to flash lamps
• Cost

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Other Laser Wire Technical Issues

• Optical Final Focus
• Operates at approximately F/4
• Commercial optics usable with little or no
  modification
• Semiconductor industry has experience with small
  spot, ultraviolet focus lenses.
• Laser Timing
• Timing requirements depend on optical pulse
  length
• Single bunch baseline system not a problem
• Multi-bunch system State of the art performance
  required.
• Detector Electronics
• Single bunch conventional
• Multi bunch Fast electronics, but within state
  of the art.

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Laser Wire Cost Model

• Bottoms up costing
• Single bunch systems use commercial lasers
• Multi bunch systems use variants of the polarized
  source laser
• Single lasers drive all IPs within 100 Meters
• IPs use commercial focus lenses.
• Clean rooms used for lasers.
• Total cost 40 - 70 Million
• Cost may be reduced substantially after RD.

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Laser RD (Source and Laser Wire)

• Source laser and Laser Wires use similar
  technologies
• Investigate laser technologies which can reduce
  complexity and cost, and improve performance.
• Use diode laser for source seed
• Greatly reduced complexity
• Limited tuning range, electrical bandwidth
• Diode pumped lasers eliminate flash lamps
• CrLiSAF laser crystal Directly produce
  required wavelength for source laser
• YbYAG laser crystal Diode pumped, high
  efficiency, directly produce short pulses for
  laser wire.

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Laser RD Continued

• Diode pumped pump lasers
• Eliminate flashlamps.
• Less technically challenging than direct diode
  pumping final laser
• Increased optics automation - reduce the need for
  expert tweaking of laser systems
• If new technologies do not perform as required
• Study performance of conventional systems
• construct conventional prototype
• Laser technology is rapidly developing - new
  solutions may be developed.

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Laser RD Plan Outline

• Laser RD partially done after CDR
• Laser System initial RD
• 1160K, 6 Man years total. FY2001-2002
• Laser System Prototype and DFM
• 875K, 7.5 Man years total. FY2003-2004

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Other beam line instrumentation

• Baseline costs estimated based on prior
  experience (top down). Most technical risks are
  small, and minimal RD is required. Total costs
  17M
• Wire scanners (conventional) 3.8M
• PIC (ion chambers) 3.1M (some RD to reduce
  costs)
• Profile Monitors 2.7M
• Stored beam loss monitors 387K
• Bunch length monitor (microwave) 260K
• Low energy polarimeter 250K total
• Farady Cup 140K total
• PMT loss monitors 48K
• Gap monitor 42K

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More Beam Line Instrumentation

• Some instrumentation requires RD
• PLIC cables - long ion chambers
• Multi bunch use requires deconvolving signal
• RD covered in the MPS section (primary use of
  PLIC)
• Estimated total system cost 3.3M
• Synchrotron monitor / Streak camera
• Need to work near resolution limit for damping
  rings
• RD underway at ATF
• Possibly use XUV / X-ray for improved resolution
• Estimated system cost 1.3M
• Tune monitor
• Prototype working at ATF
• Estimated total system cost 600K

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Yet More Beam Line Instrumentation

• Spot size monitor (Shintake style)
• Can work at secondary focus, probably not at IP
• estimated cost 2M
• Final focus instrumentation
• Beamstrahlung monitor
• Luminosity monitor
• Disrupted beam instrumentation
• Energy spectrometer
• Polarimeter
• Beam timing monitor

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Lasers and Instrumentation Summary

• Source Laser
• Technically challenging
• Critical to machine operation
• Extensive RD effort expected
• Laser Wires
• Can use source laser technology
• Expensive subsystem
• RD to reduce system costs / increase reliability
• Other instrumentation
• Many systems to be developed
• Some RD required
• No technological show stoppers