Getting to know the CERN Associated Members of Personnel (MPAs)


Part 1: USERs

A bit of history

CERN is above all an "international laboratory"[1] providing members of the particle physics community some unique installations in the world to perform "research of a pure scientific and fundamental character" and to push science forward but also serve the human kind (The Organization "shall have no concern with work for military requirements").  Most members of the particle physics community who come to CERN to conduct this research are 'Users'.

The excellence of the Organization and the scientific interest of its facilities have therefore allowed the community of Users to grow steadily at CERN to reach 11,175 persons by the end of 2021.

Evolution of the number of Users at CERN since 1970[2]


How is the User’s statute described in the Administrative circular AC 11?  

Administrative Circular No11 Rev 7.pdf (

The Administrative Circular no. 11 (rev. 7) describes all existing categories of personnel at CERN. In its articles 1 and 11, it states that ‘the Organization has two categories of members of the personnel, namely employed members of the personnel and associated members of the personnel

Associated members of the personnel are not employed by the Organization but are appointed by the Director-General based on a contract of association. In accordance with the mission of the Organization, the purpose of contracts of association is to promote a) international collaboration; b) contacts between, and the exchange of, scientists; and, c) specialized training"

Who are these colleagues?

Well, USERs can have very diverse backgrounds. Some of them are Physicists or Engineers. There are also technicians, secretaries, or communication professionals. What they all have in common is their status: They are all affiliated to an Institute collaborating with CERN.

What we call an institute, in the CERN jargon, is essentially a university or research centre that have joined a CERN Collaboration. For example, on the LHC, the four largest collaborations are ALICE, ATLAS, CMS and LHCb. When a university becomes a member of one of these, it is called an Institute. There are various types of Institutes with different rights and duties, but this is for a later article!

Once the Institute is properly registered and formally part of a Collaboration, anybody with an employment relationship with the university can enjoy the status of USER. Students, Post-Docs or faculty, all of these are eligible to come to CERN and get access to the Organisation’s infrastructure.

There are users from institutes located in the Member States, others are attached to institutes based in non-Member States; this without these Users having the nationality of the institute... Diversity is the norm here!

One might wonder why there are so many USERs at CERN and what their responsibilities are?

To answer that question, we need to go back to the governance model of Collaborations. When the LHC was being setup, it was decided that the responsibility to build and run the experiments will be mainly borne by Collaborations.

Today, CERN provide an essential support to run the LHC detectors, but the vast majority of the people in charge of the day-to-day operation, in charge of the upgrade programs, or in charge of the data analysis are USERs. Some key positions in the governance of the Experiments are reserved for CERN employed members of personnel, like the Technical Coordinators or the Resource Coordinators. These are exceptions and most often than not, the Spokesperson of an Experiment is a USER.

While many USERs only come to CERN occasionally, like to man a shift in the control room of and Experiment, or attend a meeting, some others are stationed in our region. These specialists have critical responsibilities and cannot be away from CERN. In these configurations, they relocate to the region with their families for many years at a time. To help them cope with the high cost of living involved, and to cover additional costs arising from their stay in the local area, a subsistence allowance was awarded together with an internal taxation certificate. This mechanism has ensured, for many years, that Collaborations had the possibility to cover the necessary costs to secure the critical manpower they need at CERN.

Consequently, the uninterrupted commitment of USERs is essential to the performance and even survival of the CERN Experiments. To put it bluntly, there would have been no discovery of the Higgs boson or the Z and W bosons without the Users. There cannot be a successful upgrade program without USERs. In fact, CERN is called a USER facility, which means that the Organisation is meant, by design, to rely on the USER community and has the duty to host its members. These colleagues bring with them a set of essential skills that CERN cannot do without, unless it becomes an empty shell. They make an incredibly divers population with 110 nationalities represented. The pool of talent brought by the USER community cannot be underestimated and offer the sort of diversity and creativity our Organisation needs to keep innovating and pushing the boundaries of Human knowledge.

Substantial changes

In December 2020, the Council approved the Management's proposal to introduce a new type of financial allowance, called Cost of Living Allowance (COLA).

Whereas up until recently Users received, when eligible, a subsistence allowance instructed or paid by CERN which constituted a financial benefit under Staff Rules and Regulations (SRR), with the issuance of an internal taxation certificate.

A cost-of-living allowance, which is an allowance similar in nature to the subsistence allowance, processed by CERN on the instructions of a third party (i.e. Collaborations) and which no longer grants the right to an internal taxation certificate. As a result, some of them, depending on the applicable tax rules, become subject to the payment of a tax, which they did not pay before the introduction of the COLA. Their available financial resources are therefore reduced accordingly.

The Staff Association representing all CERN personnel, including Users, has been asking for more than two years for a study of both :

  • subsistence levels, taking into account the effect of taxation due to the introduction of the COLA, but also
  •  Clarification of the eligibility criteria to be used in the context of
    • the contractual relationship between a USER and its Institute;
    • the contractual relationship between a USER and CERN;
  • with a particular focus on the treatment of financial and social issues (health insurance and pension) in order to avoid any precarious situation for our colleagues.

Having a thriving, top tier USER community is an existential parameter in CERN’s ability to succeed in its present and future missions.

We will have the opportunity to come back in more detail to the various topics discussed here in a future article.


[1] The quotations in this paragraph are taken from the Convention establishing CERN.

[2] Table taken from statistics presented by the User's Office.