Back to My Roots

My faithful readers will know 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 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.

©CERN

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

After being assured of my stay, I took the train from Freiburg to Geneva. When I stepped onto streetcar number 18, I was excited because all trams and buses flew CERN flags and those of the Open Days.

The following morning at my hostel. View of the Alps and Mont Blanc

Once I checked in, I went to see the responsible lady for the Open Days, asking whether my affiliation 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 channel the visitors in an underground accelerator pit. This was too much for an octogenarian. Besides, my presence would be more useful in helping the people of my former group explain 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 unique 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 daily walking steps.

In the evening, there was 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 mostly stood 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 also a natural source of ionizing radiation. 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 professionally exposed workers. While at CERN, people working in radioactive areas or with radiation sources wear dosemeters to determine their personal radiation doses; those to flying staff are evaluated by calculation. In fact, exposure to cosmic rays is well-known for the routes planes take routinely.

Lying in the sand

The natural exposure rate due to terrestrial and cosmic radiation in the Geneva region 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 in Kerala, India, were notorious as natural radiation sources. At 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 simultaneously 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 in dissipating their underlying angst.

The Sunday afternoon crew (©RP CERN)

The operation of a high-energy accelerator produces radiation. Radiation has become a political issue, and the CERN management has understood. So I was only mildly astonished to learn that despite 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 simultaneously satisfied, having helped my former colleagues sell 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

*