RF Compressor (SLED) Phase-Modulation to Reduce Peak Fields in the MAX IV Linear Accelerator
(2023) EITM01 20231Department of Electrical and Information Technology
- Abstract
- Modern particle accelerators need strong electric fields in order to produce high
energy particles. Such high voltages are typically reached by injecting pulsed radio frequency power through several steps of amplification. At the end, pulse compression is used to further improve the energy gain at the cost of pulse-length.
A typical pulse compression method developed at the Stanford Linear Accelera-
tor Center (SLAC) is the SLAC Energy Doubler (SLED), which modulates the
outgoing wave-envelope using either the phase or amplitude of the incoming wave.
Normal operation of the cavity dictates that the phase is shifted 180◦ at the
final part of the pulse. This thesis, however, aimed to explore alternative operation modes in order to... (More) - Modern particle accelerators need strong electric fields in order to produce high
energy particles. Such high voltages are typically reached by injecting pulsed radio frequency power through several steps of amplification. At the end, pulse compression is used to further improve the energy gain at the cost of pulse-length.
A typical pulse compression method developed at the Stanford Linear Accelera-
tor Center (SLAC) is the SLAC Energy Doubler (SLED), which modulates the
outgoing wave-envelope using either the phase or amplitude of the incoming wave.
Normal operation of the cavity dictates that the phase is shifted 180◦ at the
final part of the pulse. This thesis, however, aimed to explore alternative operation modes in order to reduce the peak field of the output while retaining as much of the energy gain as possible. Previous work was examined and a suitable, linear phase-modulation was chosen to be implemented.
In order to realize the modulation scheme, an appropriate phase-shifter and
logic controller were chosen and tested in order to determine how the new system
would affect phase-stability. Results seemed to indicate that the new system would
have no major impact on this parameter. It was then deemed appropriate to install
the system on one of the accelerating sections towards the end of the MAX IV
linear accelerator.
Results from the newly installed setup seemed to conform with the modelling
work despite certain setbacks caused by the cavities inside the SLED being out of
tune. Overall the implementation appears to have accomplished its task well. (Less) - Popular Abstract
- The modern world is dependent on our understanding of nature and how both
organisms and materials behave on the very smallest of scales. Whether the goal
is to create better concrete, batteries or vaccines one needs to understand how
things move and form in order to make way for improvements. This is why many
turn to particle accelerators, not for the particles they accelerate but from what
those particles produce.
At MAX IV electrons are used to produce very bright and fine X-rays which are
capable of resolving details down to the atomic level in some cases. These electrons need to be accelerated up to almost the speed of light. In order to achieve this they are sent down a tube throughout which they are fed energy by an injected... (More) - The modern world is dependent on our understanding of nature and how both
organisms and materials behave on the very smallest of scales. Whether the goal
is to create better concrete, batteries or vaccines one needs to understand how
things move and form in order to make way for improvements. This is why many
turn to particle accelerators, not for the particles they accelerate but from what
those particles produce.
At MAX IV electrons are used to produce very bright and fine X-rays which are
capable of resolving details down to the atomic level in some cases. These electrons need to be accelerated up to almost the speed of light. In order to achieve this they are sent down a tube throughout which they are fed energy by an injected electric field at certain stages. This field is, in fact, a radio frequency wave which has been amplified up to several kilovolts in order to boost the electrons as much as possible.
In order to achieve this level of amplification however, the field is stored in a
cavity referred to as a SLED. This cavity can be likened to a water tank where the
timing or phase of the incoming radio-wave is the equivalent to the valve. When
the phase is instantly shifted 180◦ the stored field empties quickly and you get
a short but intense burst which decays quickly. This is similar to immediately
opening the valve completely.
The problem with this method however, is that the peak field strength becomes
so high that there is a risk of discharge in the transmission line which can damage
the equipment. This can be mended by instead shifting the phase over some
short period of time which smooths over the initial spike in the burst. Correct
modulation still delivers almost the same energy amount to the electron beam.
This master’s thesis has explored the concept of phase-modulation and how
such a system could be implemented at the MAX IV accelerator. Several math-
ematical models of the process were set up and after discussion with the MAX
IV staff, a suitable phase-modulation scheme was chosen. Appropriate electronic
components were then decided upon and tested in order to determine if their preci-
sion and capabilities were good enough. Finally the system was implemented and
the results appeared similar to what was predicted by the mathematical models. (Less)
Please use this url to cite or link to this publication:
http://lup.lub.lu.se/student-papers/record/9120837
- author
- Ekström, Joel LU
- supervisor
- organization
- course
- EITM01 20231
- year
- 2023
- type
- H2 - Master's Degree (Two Years)
- subject
- keywords
- Accelerator, MAX IV, LINAC, Phase-modulation, SLED, Pulse compression
- report number
- LU/LTH-EIT 2023-921
- language
- English
- id
- 9120837
- date added to LUP
- 2023-06-08 10:32:13
- date last changed
- 2023-06-08 10:32:13
@misc{9120837,
abstract = {{Modern particle accelerators need strong electric fields in order to produce high
energy particles. Such high voltages are typically reached by injecting pulsed radio frequency power through several steps of amplification. At the end, pulse compression is used to further improve the energy gain at the cost of pulse-length.
A typical pulse compression method developed at the Stanford Linear Accelera-
tor Center (SLAC) is the SLAC Energy Doubler (SLED), which modulates the
outgoing wave-envelope using either the phase or amplitude of the incoming wave.
Normal operation of the cavity dictates that the phase is shifted 180◦ at the
final part of the pulse. This thesis, however, aimed to explore alternative operation modes in order to reduce the peak field of the output while retaining as much of the energy gain as possible. Previous work was examined and a suitable, linear phase-modulation was chosen to be implemented.
In order to realize the modulation scheme, an appropriate phase-shifter and
logic controller were chosen and tested in order to determine how the new system
would affect phase-stability. Results seemed to indicate that the new system would
have no major impact on this parameter. It was then deemed appropriate to install
the system on one of the accelerating sections towards the end of the MAX IV
linear accelerator.
Results from the newly installed setup seemed to conform with the modelling
work despite certain setbacks caused by the cavities inside the SLED being out of
tune. Overall the implementation appears to have accomplished its task well.}},
author = {{Ekström, Joel}},
language = {{eng}},
note = {{Student Paper}},
title = {{RF Compressor (SLED) Phase-Modulation to Reduce Peak Fields in the MAX IV Linear Accelerator}},
year = {{2023}},
}