Re: LASER facility questions

[rcmannix@uci.edu (Richard C. Mannix)]

>To those who are involved in Laser safety,
> I am designated LSO addition to RSO at our facility. I have been to two
>training classes four-five years ago. I forgot what I learned. We are in
process
>to setting up a class 4 laser. This system seems to be an old unit.
>
>The unit spec. are:
>    wave length (changed at the end): start at 1.053 um,  at the end it's at
>0.5265 um
>    energy (changed at the end): start at 1 J, end at <0.5 J
>    pulse duration: 50 usec

I'm not certain what you mean by "start" and "end", but this sounds like it
could be a Nd:YAG laser which emits primary radiation at 1.064 um, and can
emit radiation at 0.532 um if a "doubling" optical element is used.

Pulses in the 0.5 - 1 J range are substantial!! This radiation can cause
very severe eye damage (in this case, retinal damage).

Most Nd:YAG lasers (if that is indeed what you are dealing with) are
repetitively-pulsed. That is, they emit multiple pulses per second. You
didn't indicate whether that is the case for your laser. How many pulses are
emitted during a potential eye exposure is an important matter to consider. 

>I was told that a laser unit housing is there but need to be removed until they
>set everything up such as cooling water line leakage check and a number of
>items. This will be done while beam is on.

Whether there is a reasonable likelihood of eye exposures during this
process is the main issue. Can the laser radiation be enclosed/shielded
while this water leakage check is performed??

>Here are my questions:
>    1. What wavelength laser and power level is this? (two separate optical
>goggles and MPEs?)

Sounds like the peak power/pulse is 1 J/(50 msec) = 20,000 Watts.

You can get laser protective eyewear which can protect at both 0.532 um and
at 1.064 um. Eyewear suppliers such as Uvex (800-343-3411) can calculate the
required optical densities of the eyewear for you based upon the laser specs
you give to them.

It seems to me that in order to provide sufficient eye protection, you are
looking at optical densities of about 6 - 7. Pretty high!!

>    2. I have a ANSI Z136.1-1993. I thought a newer version came out after
that.
>Are there a
>        lot of changes in the newer version from the version I have? I don't
>mind to buy one but
>        user is in a hurry.

That is the most recent version.  Make sure that you have your laser safety
calculations checked by the eyewear company. A miscalculation could have
serious consequences!!! Find out if the laser is repetitively pulsed!!

>    3. Table 10 of the ANSI 136.1 states that NHZ analysis required for a
number
>of control
>        measures. How shall I do that?

The NHZ includes any areas in which the MPE can be exceeded. In your case,
anywhere primary or significant reflected laser radiation can be viewed
would be inside the NHZ. Only the person performing the leakage check should
be in the room at that time. Get everybody else out of there.

>    4. I was told that once set up is completed they are going to enclose the
>unit. Can it forgive
>        some safety requirements because it is going to be enclosed after a
>while?

Yes, as long as the safety features (enclosure, etc.)  will remain intact.
The hazard analysis is based on the accessible radiation -- radiation to
which it is possible to be exposed to under all reasonably-likely
applications. If the beam is completely enclosed, additional safety
requirements may not be as needed.

How competent and trained the personnel in this lab are is an important
consideration. Have they had laser safety training?? Are they qualified
senior lab techs, or perhaps undergrad students??

Make sure that all people involved are well aware of the risks attendant to
the operation of the laser. Don't try to scare them, but instill in them a
healthy respect for the laser.

Tell them that while serious laser-produced eye injuries are relatively
uncommon, the consequences of laser accidents can be tragic -- sometimes
complete loss of vision in an eye. In other words, high-power laser use is a
low risk, high hazard issue.

Also, make sure that they are competent regarding the use of high-voltage
power supplies. Only well-trained individuals should service such power
supplies. 

Rick Mannix
Health Physicist
Laser Safety Officer
Univ. of Calif., Irvine
949-824-6098
rcmannix@uci.edu