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Markus Haverkamp (promotion date: 16 October 2003)

Decay and Snapback in Superconducting Accelerator Magnets

Promotion Date: 16 October 2003

Markus Haverkamp

CERN (www.cern.ch) in Geneva are constructing a new particle accelerator, the Large Hadron Collider (LHC). The accelerator will be built with superconducting accelerator magnets. During the injection of elementary particles into the machine, the interaction between current distributions in the magnets and the magnetisation of the superconducting material results in dynamic changes in the magnetic field, called “decay” and “snapback”. These changes in the magnetic field have an impact on the beam performance of the machine and cause a loss off particles. To compensate this loss of efficiency it is important to understand the underlying mechanisms. For this reason we organised a demonstration experiment at the university to model situations typically appearing during decay and snapback.

What was your thesis about?

CERN (www.cern.ch) in Geneva are constructing a new particle accelerator, the Large Hadron Collider (LHC). The accelerator will be built with superconducting accelerator magnets. During the injection of elementary particles into the machine, the interaction between current distributions in the magnets and the magnetisation of the superconducting material results in dynamic changes in the magnetic field, called “decay” and “snapback”. These changes in the magnetic field have an impact on the beam performance of the machine and cause a loss off particles. To compensate this loss of efficiency it is important to understand the underlying mechanisms. For this reason we organised a demonstration experiment at the university to model situations typically appearing during decay and snapback. At CERN we constructed a Hall detector and used the device for magnetic measurements on real superconducting accelerator magnets. I also performed numerical simulations of the behaviour of superconducting filaments in typical situations during decay and snapback, and finally I used the results of these simulations in order to create a numerical model to calculate the decay and snapback in a coil. Ultimately, the comparison between measured and calculated data revealed correlations between the different parameters of decay and snapback.

Can you tell more about the LHC?

It is a circular particle accelerator with a circumference of 27 kms about hundred metres below ground, located between Lake Geneva and the French Jura mountains. It crosses the French-Swiss border several times.

In the LHC dipole magnets are used to bend the beam. You also have higher order magnets like quadrupoles and sextupoles etc. to focus and defocus the beam, or to control specific beam parameters.

My research was related to the dipole magnets only. In the other magnets we assume the effects to appear in a similar way.

You have been involved with CERN for a while so you perhaps you could tell:

how far are they?

The official starting point of the LHC is scheduled for 2007 if I am informed correctly. The last time I visited CERN I saw a large number of magnets stored close to the magnet test facility SM18. I do not know whether they have already started to install them in the tunnel. The CERN project has an enormous spin-off. Apart from the development of superconducting magnet technology and potential new discoveries in particle physics, the experiments will for instance need huge computing power that a sole institute cannot provide. For this reason a grid of computing centers is being developed to bundle the resources of computing power all over the world.

Do you still work for CERN?

No, I work for a small firm (www.metrolab.ch) in Geneva now, it sells NMR (nuclear magnetic resonance) equipment and equipment for magnetic field measurements. The company was founded by people who had worked for CERN and acquired their know-how there. I am mainly involved in software development for an upgrade of a present device.

Did you like to work on such a big project like at CERN?

It was very stimulating to work in such an international research environment. I moved back and fourth several times, between Switzerland, France, the Netherlands and finally Germany. This gave me the opportunity to meet a lot of people of different cultures and to learn several languages.

Is there such a difference in culture between the countries you just mentioned?

Well, for instance I think the Dutch people are less bureaucratic. That makes things easier to plan and they are more modern in a certain aspect. You can address your professor in a way that is unthinkable in Germany, and this direct way of address makes it also easier to communicate.

My group in Twente, the Low Temperature Group, were very motivated, you get things done quickly and there is a very good climate in the team.

What are your plans for the future?

At the moment I live in Grenoble in France with my future wife. She is Portuguese, we are getting married in Lisbon in May. And I am starting my job in Geneva.

Links:

My Ph.D. thesis: http://www.ub.utwente.nl/webdocs/el/1/t0000027.pdf

My M.Sc. thesis: http://haverkamp.gmxhome.de/Diplomarbeit.pdf

List of publications: http://haverkamp.gmxhome.de/publications.html

Most recent seminar: http://ab-seminar.web.cern.ch/AB-seminar/talks/AB.Seminar.mh.pdf

My employers: Metrolab (www.metrolab.ch), Universiteit Twente (www.utwente.nl), CERN (www.cern.ch), MTU München (www.mtu.de), ESRF (www.esrf.fr)

My universities: Universiteit Twente (www.utwente.nl), RWTH Aachen (http://www.rwth-aachen.de), WWU Münster (http://www.uni-muenster.de)