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Laser Safety at Fermilab

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Laser Safety at Fermilab Training General Fermilab laser safety training (this course) On-the-job equipment-specific training Eye exam Special laser eye exam When ... – PowerPoint PPT presentation

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Title: Laser Safety at Fermilab


1
Laser Safety at Fermilab
2
Blast from the past! 10/17/2007
3
Laser beam safety a complex problem?
  • Lasers are everywhere
  • They vary in every respect
  • How do we know that people are safe?

4
Laser applications at Fermilab
CDF nitrogen laser enclosure (2 lasers)
A0 photoinjector accessory table
5
Laser applications at Fermilab
IB1 GammeV experiment laser enclosure
6
Laser hazard factors - radiation
  • Intensity / Duration
  • Wavelength
  • Kind of effect
  • Threshold exposure
  • Modulation
  • CW
  • rPW
  • Other

7
Laser hazard factors - people
  • Part of body exposed
  • Eye most important
  • Body covers
  • Laser protective eyewear
  • Other
  • Pre-existing conditions

8
Laser accidents
  • RLI Rockwell Laser Institute
  • Examined 417 laser accidents
  • 1964-2001
  • DOE
  • 34 laser incidents
  • 1983-2004

9
RLI overall analysis
  • Unanticipated eye exposure during alignment.
  • Available eye protection is not often used.
  • Equipment malfunction causes many unwanted
    exposures.
  • Improper methods of handling high voltage lead to
    severe shock and even death.

10
RLI overall analysis
  • Protection for non-beam hazards is often lacking.
  • Improper restoration of equipment following
    service frequently causes undesired hazards.
  • Incorrect eyewear selection and/or eyewear
    failure are frequent causes of unwanted exposure.

11
DOE overall analysis
  • Eye exposure
  • 67 of all incidents
  • Alignment
  • 47 of all incidents
  • 63 of eye incidents
  • Immediate causes
  • Failure to verify beam off
  • Fully qualified person absent

12
Spectral distribution
  • UV Ultraviolet radiation
  • Less than 0.4 mm
  • Standard starts at 0.18 mm
  • VIS Visible radiation
  • 0.4 to 0.7 mm
  • IR Infrared radiation
  • Greater than 0.7 mm
  • Retinal hazard region 0.7 to 1.4 mm
  • Far IR 1.4 to 103 mm

13
Eye damage fcn(l)
  • UV - Cornea lens
  • VIS - Retina
  • IR - Cornea

14
Effect of l on damage threshold
15
Damage mechanisms
  • Thermal
  • Increased temperature destroys tissue
  • VIS IR
  • Photochemical
  • Photon promotes chemical reaction
  • UV far blue VIS
  • Photoacoustic
  • Thermal expansion creates shock wave
  • 10-9 to 10-5 sec
  • VIS _at_ high intensity
  • Plasmagenic
  • High E-field destroys tissue
  • Below 10-9 sec
  • VIS

16
Damage threshold (approximate)
Units of J/cm2 in exposures of 1 sec
17
Making things easier
  • Classification scheme to simplify controls
  • Class 1 (safe) to Class 4 (dangerous)
  • Likelihood of inadvertent injury
  • Low _at_ Class 1, 2 3a gt few requirements
  • High _at_ Class 3b 4 gt many requirements
  • BTW - Consumer products are usually safe
  • Read and obey warning labels
  • Dont take things apart

18
Some lasers _at_ Fermilab
  • Class 3b and 4 systems mostly physics apps
  • Class 3b nitrogen lasers to calibrate
    scintillation detectors
  • Class 4 NdYAG lasers for photon-particle
    interactions or material applications
  • Class 2 and 3a systems often diode lasers
  • Pointers, scanners alignment systems
  • CD/DVD fiber optic communication systems
    (usually enclosed)

19
Lasers in Fermilabs inventory
20
What standard do we follow?
  • ANSI Z136.1-2000
  • American National Standard for the Safe Use of
    Lasers
  • Guidance is exhaustive (and exhausting)
  • Required by 10 CFR 851
  • DOE Worker Safety Health Rule
  • Locked into 2000 version of ANSI standard

21
Some acronyms
  • LSO Laser Safety Officer
  • MPE Maximum Permissible Exposure
  • The max amount of laser radiation that doesnt
    cause a harmful effect (units are J/cm2 or W/cm2)
  • BTW The MPE is a complex function of
    wavelength, modulation exposure duration
  • NHZ Nominal Hazard Zone
  • The space within which the MPE is exceeded
  • Includes direct, reflected scattered radiations

22
Reflections
  • Specular
  • Mirror-like
  • Irregularities ltlt l Smooth
  • Angle incidence Angle reflection
  • Diffuse
  • Fuzzy
  • Irregularities gtgt l Rough
  • Max reflected normal to surface

23
Different kinds of laser people
  • Laser operators People who operate laser
    systems that emit harmful levels of laser
    radiation.
  • Spectators People whose access to potentially
    harmful levels of laser radiation is controlled
    by the laser operator.

24
More roles
  • The Public People who must be isolated from
    potentially harmful levels of laser radiation
    because the laser operator cannot control their
    access.

25
Lasers by hazard class
26
Class 1
  • Description
  • Any wavelength (meaning 0.18 to 103 mm)
  • Over 8 hrs of direct eye exposure to cause injury
  • 40 to 400 mW for visible CW lasers
  • Precautions
  • Usually none
  • But watch out for the following
  • Disassembly if enclosed laser has higher hazard
    class
  • Modifications that may increase the hazard class

27
Class 2 - description
  • Visible wavelength beam (0.4 to 0.7 mm)
  • Over 0.25 sec to cause eye injury
  • Up to 1 mW _at_ CW
  • Depends on aversion response

28
Class 2 - precautions
  • Do not stare into the beam
  • Do not point the beam at people or shiny objects
  • Maintain separations for public displays
  • Precautions for Class 1 lasers apply

29
Class 3a - description
  • 1X to 5X Class 2 limits for visible radiations
  • 0.4 to 0.7 mm
  • Up to 5 mW as long as lt2.5 mW/cm2
  • 1X to 5X Class 1 limits for invisible radiations
  • UV (lt0.4 mm)
  • IR (gt0.7 mm)

30
Class 3a - precautions
  • Do not view the beam directly with optical
    instruments
  • Precautions for Class 1 and 2 lasers apply

31
Class 3b - description
  • More than Class 3a but less than 0.5 W
  • Immediate eye hazard
  • UV less than 1.6 hours
  • VIS less than 0.25 sec
  • IR less than 0.1 to 0.9 sec

32
Class 3b - precautions
  • Avoid eye exposure to direct or reflected beam
  • Review approval by LSO D/S/C
  • Qualify laser operators
  • Isolate people from the beam
  • Post signs during unenclosed operation
  • Consider laser eye protection (optional)
  • Other

33
Qualify laser operators
  • Laser operator
  • Qualification
  • Laser safety training
  • Laser eye exam
  • Laser system manager authorization

34
Training
  • General Fermilab laser safety training (this
    course)
  • On-the-job equipment-specific training

35
Eye exam
  • Special laser eye exam
  • When
  • Prior to initial participation
  • Following suspected harmful exposure
  • Termination of work at Fermilab
  • Coordinate through Fermilab Medical
  • Wilson Hall Ground Floor NW / X3232
  • Exam actually done offsite at eye clinic

36
Isolation
  • Goal Keep people away from harmful levels of
    laser radiation
  • Best An enclosed light-tight laser system box
    that qualifies for Class 1 status
  • Good Open laser beam(s) in a light-tight room
    with only qualified allowed inside
  • Weak Unqualified people kept away from open
    laser beam(s) in a way that relies heavily on
    common sense and trust (e.g., safety tape)

37
Isolation box or room
  • Goal Reduce hazard class
  • Usually aim to drop Class 3b/4 to Class 1
  • Enclose as much of beam path as possible
  • Fiber optics can be part of enclosure
  • Good enough radiation tightness - OK
  • Enclosure must be locked or interlocked
  • Added benefit protects your laser set-up

38
To lock or interlock?
  • Locked enclosure (typical for box)
  • Tool required to open enclosure (can be a key)
  • Warning message also required
  • Label(s) on box
  • Sign(s) on room door(s)
  • Objective opening enclosure must be deliberate
    act
  • Interlocked enclosure (typical for room)
  • Opening enclosure turns off beam

39
CDF laser box - locked
40
CDF laser box - open
41
Signs
  • Recommended designs
  • Post where they will best warn potentially-exposed
    people (e.g., doors)
  • Avoid long-term posting
  • People will learn to ignore warning
  • Magnets, velcro, illumination

42
Signs labels
43
A0 laser room entrance
44
Laser eye protection
  • Dl optical density _at_ wavelength l
  • Hp potential eye exposure
  • MPE Maximum Permissible Exposure

Dl log10(Hp/MPE)
Get help from LSO, online applications, and
eyewear distributors.
45
Estimated exposure duration
Suggested exposure times for eyewear design. Use
actual times when known.
Values are taken from ANSI Z136.1-2000
46
Other
  • Exercise special care
  • During alignment
  • With invisible beams
  • Where people not involved in the operation can be
    exposed to the beam
  • Precautions for public displays apply
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