Effect of Insertion Devices Tapering Mode of Operation on the MAX IV Storage Rings

Abstract

Tapering is a mode of operation of insertion devices that allows the users to perform scanning in a range of photon energies. NanoMAX, BioMAX and BALDER are all beamlines of the 3 GeV MAX IV storage ring and will provide this special mode of operation for their users. In this thesis, the spectra of NanoMAX and BioMAX while operating with tapering were studied and feed forward tables that cancel out the closed orbit distortion caused by the insertion devices were generated. Moreover, a study of the nature of the closed orbit distortion was performed, aiming at simplifying the feed forward table measurements that can currently be quite time consuming. In addition, the effect of BALDER, which is a wiggler and currently the strongest insertion device in the storage ring, on the electron beam was studied. Apart from the feed forward table that corrects for the closed orbit distortion, BALDER induces a beta beat and tune shift which has to be eliminated in order to make the insertion device transparent to the electron beam. This correction is needed in order to keep the beam life time unaffected and ensure a stable operation. For this reason, a two-stage correction scheme was proposed. First, a local correction with the quadrupoles adjacent to BALDER was performed in order to eliminate the beta beat induced by the wiggler. As a second step a global correction was applied. The aim of the global correction is to bring the tune back to the design values.

Popular Abstract

Accelerators are huge machines (up to tens of kilometers long) dedicated
to accelerate particles, such as protons and electrons, up to very high energies
which makes them travel almost with the speed of light. Worldwide there are
many different types of accelerators used for a wide range of applications and
research. CERN is probably the most well-known research center related to
accelerators in the world. At CERN, there are mostly high energy physics
experiments running with accelerators called colliders, named after the particle
collisions that occur in this case. This means that the purpose of those collisions
is to seek answers to fundamental questions, such as which are the blocks that
the universe is made of.
On the other hand, MAX IV uses accelerators for different reasons. Electrons
are accelerated in order to produce light which makes MAX IV a big photon
factory. This type of accelerator is called a light source and it is more common
than colliders. The photons are produced in magnetic devices called insertion
devices and they are X-rays, like the rays used in the airport security. However,
the intensity of the X-rays produced in this case is huge and hence, they can be
used for experiments of a great variety. For example, by using this light we can
study the structure of proteins. This information can explain their functions
and therefore, it will offer an insight into how human body works. In addition,
the light produced can be used for research in many other disciplines such as
material science, environmental science and archeology.
Some experiments running at MAX IV require light of very specific prop-
erties. Normally, the insertion devices consist of a large number of pairs of
magnetic poles, like earth has the north and south pole, which are placed in a
constant distance from each other. This leads to two girders with magnetic poles
parallel to each other. However, in order to produce this different type of light
the two girders of the insertion device must not be parallel to each other but
open like a fan. This mode of operation is called tapering mode. The spectrum
of the light produced in this case consists of high intensity light that consists of
a wide range of energies. Therefore, this light is not as monoenergetic as before
and it can be used for scanning within a range of energies when the optimum
energy for the experiment is unknown.
However, using the insertion devices in both normal and tapering mode
produces a magnetic field that disturbs the electron beam and hence all the
experiments running in the laboratory. For example, using this mode without any correction applied can possibly ”kick” the electrons outside of the aperture
of the accelerator in which electrons can move. In this case the electrons would
be lost and no experiment would be able to run. The first goal is to test and
offer the tapering mode to the experiments at MAX IV. Afterwards, the orbit
of the electrons is corrected back to the desired one when the insertion devices
operate both with tapering and without. This correction can establish that the
electrons are in the right design orbit along the accelerator and therefore the
experiments at MAX IV are running without problems.

• author: Paraskaki, Georgia
• supervisor: Hamed Tarawneh; Sverker Werin
• organization: Department of Physics; MAX IV Laboratory
• course: MAXM30 20181
• year: 2018
• type: H2 - Master's Degree (Two Years)
• subject: Science General
• language: English
• id: 8946549
• date added to LUP: 2018-06-08 10:13:49
• date last changed: 2018-06-08 10:13:49