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Frank Simon | MPI for Physics | Germany

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Derailed Schedules

There is something every experimental particle physicist has to learn sooner or later: Even if there is a detailed schedule, always stay flexible! This is especially true when you are working at test beam facilities. I learned this during my very first weeks as a particle physicists more than a decade ago, while I was still an undergrad and just started to work in a research group a bit besides my studies. The time slot for the first beam time I participated in shifted several times, due to schedule changes and accelerator problems. Back then, I did not care: When things were “go”, we loaded our stuff into the car and drove to CERN.

But of course the resulting life style, the unwillingness (or even inability) to plan things like vacations and days off is something that annoys in particular partners and family to no end. Here, my wife is no exception. In particular since she has to plan her vacations six to twelve months in advance. She is working as a pharmacist, and there always has to be one in the pharmacy whenever it is open, requiring quite rigid personnel planning. That very often is incompatible with my schedule (or lack of schedule, for that matter).

My students are now also learning this: Last week, we were supposed to take data at the CERN SPS. But due to the failure of motors on so-called TAX (Target Absorbers) blocks, the start of beam operations in the test areas at the SPS is delayed by more than a month, completely derailing our well thought-out test beam plans.

The TAX blocks are massive pieces of iron, aluminum and copper, which can be moved in and out of the particle beams. They are important components, since they can block beam to enter certain areas of the experimental hall, and are used to control the size of the particle beams. They are key pieces for the overall accelerator safety system, so without them working properly, no experiments can take place. And repairing the motors is a tricky procedure: Since the TAX blocks absorb high fluxes of beam particles, they are highly radioactive, requiring careful planning of any work being carried out to limit the exposure of the technicians performing the work. So everything has to be diagnosed and understood before people go in and do something. It is also important that the real reason for the failure is understood, to avoid it from happening again. If a motor fails again after beam has started, repairs will not be possible for several months, which would completely stop test beam experiments for this year.

Lars, one of my PhD students, during the installation of our timing experiment in the CALICE Tungsten HCAL at the CERN SPS: The only missing piece now is beam.

At the moment it is unclear how the experimental schedule will develop – Also the plans for the later part of the year will probably be rearranged, but before the accelerator is back in operation, everything is speculation. The CALICE Tungsten HCAL is fully ready for beam already, and last week, right before the CALICE collaboration meeting at CERN, my students also installed our timing experiment in the experimental hall. So all we now need is beam time… And that might come at short notice, and at other times than originally anticipated. I guess quite a bit of flexibility will be needed over the summer!

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