Wednesday, September 18, 2019

Back to My Roots

My faithful readers will know that I spent most of my professional life at CERN, the European Laboratory for Particle Physics.

Alumni welcome 2019
You may also have read that I helped to launch the union of CERN alumni last year participating in its baptismal celebration called First Collision. In fact, in the life of a particle collider, the most exciting moment is when physicists observe the first collisions.


So it was quite natural and nearly compulsory that I volunteered when the alumni were asked to help with the CERN Open Days 2019.

After I had assured may stay I took the train from Freiburg to Geneva. When I stepped on to streetcar number 18, I became already excited because all trams and busses flew flags of CERN and of the Open Days.

The following morning at my hostel. View of the Alps and Mont Blanc
Once I had checked in, I went to see the responsible lady asking whether my affiliation for the Open Days may be changed.

The LHC is shut down until 2021 for an upgrade to reach its final energy of 14 TeV
LHC superconducting magnet string underground.
You barely see the curvature of the ring tunnel.
Initially, I was scheduled to help in an underground accelerator pit channeling the visitors. This was a little too much for an octogenarian. Besides, my presence certainly would be more useful helping people of my former group explaining the mysteries of ionizing radiation. Rachel also helped me establish a CERN computing account. This was more complicated - safety oblige - than 20 years ago.

Then I started exploring my former place of work.

A development I lived through. I frequently had coffee with Robert Cailliau.
I only knew that Werner Heisenberg was a table tennis champion.
A special coffee only found in the Geneva region, the renversé
Later I was busy registering correctly (CERN Badge), and getting my gear for the Open Days (T-shirt and name badge) easily surpassing my target, the number of steps of my daily walking.

In the evening: a reception for the alumni helping with the Open Days
 at the tennis club "Le Smash". Note the white cylinder hanging from the wall:
An RP radiation monitor (see text below)
The Saturday morning Radiation Protection crew waiting for visitors.
In front right: one of the radiation measuring instruments on display (©RP CERN).

While we were waiting at our stand at 9:18 a.m. for our first customers
there was already a waiting time of two hours to visit the ATLAS experimental area.
Unfortunately, this was not the case when fulfilling my duty at the Radiation Protection Stand during the Open Days. There I was mostly standing to explain to visitors in my languages what natural radioactivity is and that eating a banana increases your personal radiation dose by 0,1 μSv*. This is due to the high potassium content of the fruit containing the naturally present radioactive nuclide 40K.
*Sievert (Sv) is the SI-unit when measuring radiation. This is a big unit, so in radiation protection doses are expressed in mSv, μSv or even nSv

Bananas are good for your health
It was new to many visitors that they are a natural source of ionizing radiation too. Two people cuddling up for a night irradiate each other mutually with a dose of 0,05 μSv, i.e., eating half a banana.

Being on a plane from Europe to the States exposes the occasional passenger to a dose of 50 μSv due to cosmic rays. Doses to flying staff accumulate, so pilots and cabin crews are in the category of professionally exposed workers. While at CERN people working in radioactive areas or with radiation sources wear dosemeters to determine their personal radiation doses, doses to flying staff are evaluated by calculation. In fact, exposures to cosmic rays are well known for the routes planes take routinely.

Lying in the sand
The natural exposure rate in the Geneva region due to terrestrial and cosmic radiation is about 70 nSv/h, but there are regions in the world where exposure to terrestrial radiation is higher. In my time at CERN, the sands from the beaches at Kerala in India were notorious as natural radiation sources. On the exhibition, we had worse. The sand from a beach at Guarapari, Brazil, gave a dose rate of 230 nSv/h. This is due to a high concentration of natural Thorium. They operate Thorium mines in Brazil. Would Einstein go to Guarapari beach? Definitely.

On the evening of the first Open Day
The RP exhibition focused on sources of natural radiation explaining at the same time that professional exposures and radiation doses from CERN activities to the population living on and around its sites are negligible, CERN's "activities" only contribute infinitesimally to doses from natural sources.

All these demonstrations were very popular with our visitors and in most cases extremely useful to dissipate their underlying angst.

The Sunday afternoon crew (©RP CERN)
The operation of high-energy accelerator produces radiation. Radiation has become a highly political issue, and the CERN management has understood. So I was only mildly astonished to learn that in spite of restrictions on personnel at CERN seventy people are presently working in RP-Group while when I retired, we had a staff of about fifty.

At the end of those highly successful Open Days at CERN, I was tired, but a the same time satisfied having helped my former colleagues selling our trade to the visiting public.

Drinking my well-deserved craft beer
in the evening sun at the terrasse of the CERN restaurant.
Full moon: Goodnight and goodbye CERN

1 comment:

  1. Before going to install an instrument at KEK High Energy Physics laboratory at Mt. Tsukubs, Japan back in 1984. I had to have a crash course on radiation and had to wear 3 radiation badges! The instrument I was installing was used on the electrons and not the nucleus, so once the beam was shut down the radiation also stopped whereas on the nucleus rings, the radiation would last for a couple of days and disperse in all directions. Likely they were installing a 4th ring while I was there and the accelerator was shut down. So I received more radiation from my flight over then while I was there. The training was still invaluable and I also enjoyed your explanation in this article. Thanks