Remember when you were learning to drive a car? It seemed incredibly difficult – recalling which pedal to push or lever to move, while still keeping a close eye on the road ahead seemed more than the human brain could cope with. So imagine how trainees learning to run JET feel: How could one possibly feel confident enough about all the systems that go together to make the world’s largest fusion experiment?

For a start, the task of “running” JET is divided between two roles, the Session Leader and the Engineer-in-Charge, both of which are rostered between a number of qualified people. At a broad level the session leader is in charge of the scientific aims of the experiment, while the Engineer-in-Charge makes sure that the systems are functioning properly and are used safely. JET’s operation is organised into scientific campaigns which are around six to twelve months long. A campaign consists of a series of experiments, each of which might span over a number of days – a day comprises two shifts, each with a separate Engineer-in-Charge and Session Leader.

Session Leader and Engineer-in-Charge

In a given shift the Session Leader’s role is to work towards the current experimental goals, picking up where the previous shift left off. To do this they need to be not only accomplished physicists, they need to understand the current experiment, and they need to know what JET is capable of. For instance they need to know how to create the type of plasma scenario required for the experiment. The Engineer-in-Charge oversees the systems as they execute the plan of the Session Leader, ensuring everything is safe for both equipment and personnel. They have the ultimate authority over JET during their shift, and take advice from engineers from all the different areas: power supplies, gases and vacuum systems, heating systems, measurement systems and the computer systems – both safety systems and data acquisition. In actuality the lines blur somewhat and the two roles cooperate closely, says Dr George Sips, from Operations in the JET department, who runs part of the Session Leader training. “Session Leaders have to be creative, to do as much as you can with the machine, but within safe limits. The Engineer in Charge can’t check every single thing; they have to rely on the other person!” Coordinator of the Engineer-in-Charge training, Stuart Knipe, also emphasises the flexibility required of the Engineer-in-Charge in the face of a creative session leader: “It’s an experiment; things change, it’s not always black and white, you need to use your nous and your engineering intuition.”

Extensive trainings

Both training regimes are extensive and include lectures, practical exercises and then an extended apprenticeship of sitting alongside a range of experienced staff to watch and learn, and then gradually taking the reins. There is not a regular intake for trainees, as it can be difficult to find a good time to schedule a training programme. However when the numbers of Session Leaders or Engineers-in-Charge begin to decline, then a call is issued, often during the lower intensity times such as a maintenance shutdown. Says coordinator of Engineer-in-Charge training Dr Stuart Knipe. “We put a call out to department managers to nominate people who are capable, available and willing.” The trainee Engineers-in-Charge receive 32 lectures over a six month period, and then sit in on ten shifts with different Engineers-in-Charge.

“I love working on the machines and being in the control room.”

Eva Belonhy

In contrast the 24 Session Leader lectures and ten hours of practical exercises are grouped into a week-long training at JET to allow for scientists from all around Europe to take part. They too then spend ten to fifteen shifts alongside experienced session leaders learning the ropes. This means the training has to be conducted just before an experimental campaign commences so that the trainees are able to gain as much experience as possible throughout the full length of the campaign. “It’s quite a daunting task, the first time they see the 17-page spreadsheet of checks and balances that they have to type in as a session leader!” says George Sips. Session leaders are drawn from a range of backgrounds, he points out. “Some are technical, while others have the scientific know-how, and others are software modelling whiz-kids”. Similarly the Engineers-in-Charge could come from any area of JET, for example diagnostics, cryogenics, beams, or active gas handling.

“I enjoy working on MAST, and to learn the complexities of JET was a clear step forward.”

Luca Garzotti

Strong teamwork

To gain the breadth of knowledge required for these roles requires a big commitment. Engineers-in-Charge are expected to do at least two shifts per week. Session leaders, generally only have one shift a week, but even this amounts to a heavy load, says Dr Sips. “Typical preparation for a session is one to two days, then a day in the control room, and then reporting to the meetings afterwards.” Of the forty-five Session Leader trainees in the 2012 program, only the best ten were taken. This qualifies them to run only simple plasmas, less than 2.5 Mega amperes plasma current – to gain a full licence, to run plasmas up to four mega-amps takes another 2 – 3 years. Despite the well-rounded training program, people have individual strengths and weaknesses, and the success of the experiment is very much a product of strong teamwork between the two roles. In fact the Engineer in Charge training even includes a lecture from experienced session leader Peter Lomas entitled “Understanding the Session Leader”. Says Stuart Knipe: “A big part of it is interacting with the people, to get the maximum out of the session.” It can take over a year to become a qualified Engineer in Charge, but Dr Knipe says the thrill of running the world’s largest fusion experiment is worth it. “It takes a lot of your time, but it’s a fun role!”

Phil Dooley, EFDA