Laser Safety at Jefferson Lab

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Orientation Objectives

• Fundamentals of Laser Operation
• film laser classification system
• Overview of ANSI Standard for the Safe Use of
  Lasers
• Biological Effects of Overexposure to Laser
  Radiation

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Incandescent light source
Laser light source
1. 2. 3.
1. 2. 3.
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Medical Approval Form
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CDRH/ANSI Hazard Classification

• Class 3a
• These lasers can be visible, IR or UV.
• Direct viewing may cause eye injury.
• Laser power is lt1 mWatt
• Class 3b
• These lasers can be visible, IR or UV.
• Direct and indirect viewing may cause eye
  injury.
• Laser power is between 5 and 500 mWatt

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CDRH/ANSI Hazard Classification

• Class 4
• High power lasers
• Direct and Indirect Viewing Hazard
• Fire Hazard
• Laser Power is gt500 mWatts
• Special Considerations
• invisible beams
• frequency doubled lasers

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Conventional Lasers

• CO2
• nitrogen
• argon
• diodes
• FIR
• excimers

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Free Electron Laser Facility

• Tunable Infrared Laser
• medium occupies below grade area
• 6 user labs on upper level
• FEL Control room/center for laser ops

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FEL Theory
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Jlab FEL Schematic
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FEL Specifications
CW Operation
Average
Power 600-1000 W Wavelength range
6.5-3 µm Micropulse energy 25
µJ Pulse length 2 ps FWHM nominal
PRF 37.425 MHz, 18.7125 MHz
Bandwidth Fourier transform limited (
0.2-0.5) Beam diameter at lab down to
100 microns Pulsed Operation

Planning to develop the capability of pulsed
operation at rates from single
pulse up to 5 kHz.
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Eye Physiology
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Conventional Laser Safety Program

• Responsibility/Authority
• Procedures
• Required controls
• User Qualifications

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Responsibility/Authority

• Laser Safety Officer
• Laser System Supervisor

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Procedures

• Laser Standard Operating Procedure
• (LSOP)
• Author LSS
• Approvals Management, LSO

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User Qualifications

• General laser safety orientation
• Laser Specific safety training
• Medical Approval

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Class 3b Required Controls

• Same as Class 4 with two exceptions
• 1. interlocked smoke detector not required
• 2. crash button not required

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Class 4 Required Controls

• Smoke detector interlock to laser power
• Entrance door interlock to shutter or power
• Yellow beacon inline with power
• Crash button inside and outside the laser area
• Emission time delay 10 second minimum
• Approved schematic of safety interlock system

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Special hazards associated with the FEL The
Accelerator

• accelerator hazards
• vacuum
• ionizing radiation
• high voltage
• cryogenics

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Special Hazards Associated with the FEL User
Lab Issues

• User equipment
• Power levels
• Picosecond pulse structure
• Harmonics
• Tunability
• Vacuum

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Power
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Picosecond Pulse Structure

• Existing ANSI standard does not address MPEs for
  picosecond pulses
• picosecond pulse structure may be more efficient
  in causing injury

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Harmonics

• Estimate 10-h ,where h is the harmonic.
• Estimate because harmonics may be lowered by
  optical transport system
• some data suggests increases in estimates
  associated with the higher harmonics

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Tunability Laser Safety Goggles

• KG3 material
• window at 2.7 microns
• mitigation
• 1. find a material that absorbs at 2.7 microns
  and sandwich it to the KG3
• 2. for now, no lasing at 2.7 microns

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Vacuum Issues

• Must transport beam in vacuum to minimize effects
  of CO2 / H2O on the beam
• Optical transport system user interface is vacuum
  window
• window must be protected to avoid loss of vacuum

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Special Hazards Associated with the FEL
Personnel Issues

• Two categories of experimenters/Safety Cultures
• Jefferson Lab Employees
• Users

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User Labs Additional Controls

• Robust laser safety interlock system
• FEL control room with permissive to user shutter
• video camera monitoring
• Experiment Approval Process

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Bootstrapping An FEL Laser Safety Program

• Benchmarking
• Peer Reviews
• Laser Expert audit

meetings meetings arguments
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Benchmarking

• Information gathering from other FEL facilities
• Drawing on past experience
• audit of three high energy laser labs

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Reviews/Audits

• Accelerator Readiness Review
• Personal Safety System Review
• Laser Safety System Review
• Anteon Audit