Accelerators

[Rennhack]

Lessons Learned: Accelerators

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[moke]

An accelerator or Atom Smasher is a great place to broaden ones horizons since some of the greatest minds in high energy physics must coexist with the health physicist thus forcing this interesting interface.

Please remember that there is no HP Program without buy in form the worker. In today's realm, I have found that when you align yourself together with the work crew you will become much more successful than if you alienate the crew. Traditionally, some health physics programs rule with a hammer vice the Team approach. Consider your present approach if you use a hammer.

I now understand that the photomultiplier tube and scintillation detection process is ever so important regarding imaging to capture the result such as with colliding ions. Huge detection systems containing hundreds of PMT's orientated at the point of collision are able to help physicists further unlock subatomic mysteries.

For the RCT, its a humbling experience to work with those who know a 1000 times more about the atom than you, at the same time, there is much to learn if one has an open mind. Think before you speak and life is fine. BS your way through and you are cooked. Together, in most cases, the alliance is strong.

If there is one lesson I learned, it was the fact that YOU MUST ALWAYS ACCOUNT FOR THE GAMMA PHOTON AND UNDERSTAND THAT YOUR SODIUM IODIDE DETECTOR IS KEY. Additionally, one must incorporate scaling factors to account for the Gamma Component when counting smears. In most cases, you will scale the Gamma against the Beta component. Your program is only as good as the forecaster.

A Tennelec or an equivalent automated Alpha & Beta counting system will do yet Gas Proportional Detection devices are no match against a NaI(Tl) detection system when hunting for a photon. NaI(Tl)is supperior for Gamma detection yet energy dependent.

When releasing material with inaccessible surfaces, one might consider the use of portable Gamma Ray Spectroscopy Units such as ISOCS or NaI(Tl) couting systems. In some cases, you musty incorporate Gamma Spectroscopy, Process Knowledge (Be careful with this subject) and HP Supervisory Evaluations as part of the Material Release Process for Unconditional Use.

Tritium is a bybroduct of many processes at accelerator facilities. And depending upon the subatomic particles used, there are a host of isotopic possibilities.

The use of activation tables against various material types interacting with specific particles may be used to forecast the outcome or resulting types of radioactivity.

Lesson: Always include a photon detection device as part of your arsenal.

Visit www.bnl.gov for an overview of the Worlds Most Powerfull Machine! The Relativistic Heavy Ion Collider here at Brookhaven National Laboratory brings huge promise within the Science Community that many are proud of.

NASA just unveilled its Space Radiation Program here at BNL that will focus its energy toward the study of Radiation Protection Against our Astronauts in Space. They will do what it takes to identify those materials that may be used to attenuate cosmic and other rays to incorporate supperior shielding media into newly developed PPE to protect space voyaging personal during our journey further into space!

The new Neutron Spallation Facility located in Oak Ridge, TN will also allow us to continue numerous studies using the elusive Neutron to exploit various materials.

Have an Awesome New Year!

Moke

[mikeland]

As always, Moke has given some good advice!  

My accelerator experience is a little different, you could
say 'jaded'.
A key number of points I would like to raise in any
environment is safety - and respect for your fellow staff.
If you are not following the ball, then you shouldn't be
there.
If you are around people and researchers who don't know
their stuff, are incompetent, or grossly slack - then you
have some quick decisions to make.
If you have little confidence in those around you in them
protecting their own safety, little along your own - then
yours is of course on the line, and it should be your
Primary concern. Some annual doses in such places can in
fact be significant.

So for young pups going into nuclear accelerator physics
research - here are a few tips.
Look at the researchers that you will be working with very
closely, as the key to any academic institution is of
course politics.
If you are in with a good crowd at a good place - then you
are lucky.
A point here is that in most systems . students/researchers
are generally brought in to the accelerator complex to
undertake their experiments for a short perod of time,
which is operated by professionals (cross fingers) at some
facility ... be very very cautious of the ones run by
academics ... if you chose this option - you will spend a
lot of time in such a place.
Be cautious of those who maintain their own independent
badge monitoring ... in my case we were using TLDs to
measure gammas - but were totally missing the neutron
component, and since we were usually producing equal
quantities of gammas and fast neutrons - dosimetry
implementation and throughness becomes very important.
Look at where the background badges are stored - inside the
accelerator complex is a big 'no no'.
Remember, you are not dealing with thermal neutrons - but
fast ones.
Lots of new words and concepts such as .sky-dose. will come
in to play . find the safety manual for such a place before
you sign up . if it is Spartan and old . you have some
ideas to keep in mind.

First inspection should be a quick stroll over to the
safety cabinet (I cannot stress this _enough_) ... if they
are missing gloves, respirators and suits (or none at all
in the first place!) ... or there is a junk collection of
non working home-made neutron detectors, non working
electronics ... and an old Bicron prospectors Geiger
counter sitting there, with a funny head on it - re-
evaluate things. Promptly.

Likewise - every person reporting in should get a badge -
and have it recorded _regardless_ of any operating
conditions, flights of fancy . or who they are!
Radiation zones should be _explicitly_ explained and
marked ... all scheduled runs, zones, beam current in
nanoamps (or unfortuantely in near mA) and charge species
used, along with all present, should be recorded in the
control room log (_meticulously_) - which should be
countersigned ... by those present. It has paper - fill it!

[mikeland]

I saw one occasion where the safety doors would close due
to neutron radiation in a hall reaching a
safety .detection. threshold, when the accelerator wasn't
on (most curious!)... those in charge assumed that there
was no radiation present ... so the controls were
physically bypassed to 'hotwire' the doors open.
This was the case for several months before they were
attended to ...
The complexes 'Licence' to operate should have been
instantly revoked ... however it was more indicative of the
staff operating and working in the place.

Staff should never be in fear of their jobs or careers for
raising _any_ safety concerns (no matter how trivial) - I
know this is a little moral of mine ... however the real
world doesn't work like this - It Should!
Most places have had their share of .accidents., recorded
or not. A lot of the older staff may be blasй about the
doses they receive . again astuteness should be a word on
your lips.  

Radioactive materials is a next area to look into -
unlicensed (open)sources within or sitting on unlocked
safes crammed ajar full of multiple Curie materials should
be a good warning sign of things and places to avoid ...
along with loose hot materials lying around in various
nooks and crannies ... there is no point sitting next to
something such as a safe without labels on it for half an
hour and then finding out later that the needle on your
meter buries near it ... ... and your TLD doesn't match
later ... oops~!

There is also no point finding a hot particle on your glove
one evening and not knowing where it came from ... then
doing a sweep and finding drums of unsealed bagged
materials stashed around the corner ... most universities
have little goodies hidden away in all sorts of places,
recorded or not.

Next we come to the accelerator ....

Most complexes have more than one accelerator - along with
the main beam assembly depending on whom they purchased it
from (some/most in antiquity) ... usually there is a large
target floor with multiple beam lines for targeting
selected charge states ... and various target lines running
to experiments.
Shielding should be present around beam dumps - hydrogenous
materials such as boron in wax being the key here ... don't
think - look for them!

The place should be tidy, clean and well kept - with
equipment stashed neatly away ready for operation.
Also watch out for smaller accelerators ... they should be
in their own little bunkers - with their own rad detection
systems and 'on' lights visible from outside.
There is no point being near these when they are on ... or
having them stationed near where people are working
especially when there is a 4 by 2 gib wall between your
environment and the 'baby' accelerator next door.    


All accelerator meters should be fed back to the control
room for real time monitoring - and results be available
and entry points to any complex ... remember with pulsed
beams - the initial flux can overcome the sensitivity of
wall mounted (.homemade. (yet another thing to watch)
detectors ... due to the nature of the response time of the
electronics in their circuits - and the nature of the tubes
themselves . interacting with the beam pulses.
Most beams are pulsed for gamma spec purposes . with
general timing resolutions of sub 50 nanoseconds being
achievable. Having staff working on detectors while firing
a beam down is not good . all electronics should be
calibrated remotely.
A small trick for young players.  

The Control Room - accelerator 'beam time' should be
clearly marked out - and should be stuck to - period.
Beam currents should be kept low as reasonably
achievable ... there is no point running high charge state
low Z materials and causing excess generation of products
(directional neutron fluence here ... watch out!) .. that's
just plain _dumb_. An often seen event ...  
Have the best detectors that you can lay your hands on - if
you can't afford them - why bother running in the first
place?

[mikeland]

Oh - and strictly no entry into the accelerator hall while
the beam is on - even with the beam stops in! Period!
Buttons have a habit of becoming pushed at the wrong times,
by the wrong people.

The next area of interest should be your experiment - and
your targets and environment - they should be treated as
hot at all times ... going to eat your lunch after
assembling things and not washing/scrubbing your hands is a
big no no! Safe habits are good ones - and try retraining
an academic later who thinks that he/she knows best?
An accident waiting to happen - it won't happen over night -
 but it will happen.  

Vacuum lines and compressed dry nitrogen lines - along with
turbo vacuum pumps and liquid nitrogen sources are also to
be respected.
Along with when handling liquid Helium - which can become a
superfluid ... not to mention that a lot of fission
fragment detectors utilise high Tesla field strengths ...
caution is a good word!  

Our next tiki tour will be to a linac apparatus - short for
linear accelerator hall - which consists usually of
cryogenic beam 'pumpers' which utilise resonance to up the
beam energy ... these of course pump out hard x-rays ...
and should not be remotely operated on a computer system
that is NOT accessible from outside the control room ... it
is likely to severely displease those working on them - as
they may assume that the accelerator complex is not
working - and not wear their badges ... (see above) - when
some tech ramps 'them'. Been there.

Again - I cannot stress enough on real time meters -
personalised (www.gammascout.com - now with built in
presetable audio alarm and logging) - there are no prizes
for stupidity, or reinventing the wheel - and Assumption is
the Mother of All Stuff-Ups.
If you have to buy your own Gammascout ... you shouldn't be
there in the first place!

Now - shielding for high energy fission or fusion fragments
(100's MeV+) may present a number of HP issues for those
working on various parts of the apparatus of the
accelerator in general - not to mention down-range while
on!!!!
But if you are near these - you shouldn't be there at
all ...
Also - a number of other research activities are carried
out - such as neutron bombardment - heavy ion bombardment
(sometimes radioactive species beams!), generating a number
of short half life species, that may be held in receptacles
that are not designed to hold these materials ... you know
the drill.
Also - for assay work - lots of sediments and materials are
sampled (usually historic C14 from timbers/biologicals)- do
watch out for other TU species accumulating on charge
strippers and 'corners' - along with general splatter
zones. Especially if it is sediment studies from around
Mayak in Russia ... or elsewhere ... low level atomised
Pu239/Am241/Po210/U236/Pu24x on the cuffs doesn't help when
you think you are having a good day in a relatively clean
accelerator environment!

One final check ... if you look at the safety licence report
for a place (it should be available for all to see!). and
find that it has been signed off by those working there .
and they.ve based it on old stuff prehistoric calculations
only and not on real measurements ... run!!!  

Anyway ... there are a few more things I.ve probably
forgotten that someone will mention at some point.
Shop around where you want to work . not all places are
equal, or staff as concerned about safety and research as
they should be, or you'd prefer them to be!!!
When you find somewhere good ... have fun!!!