A Hardware transverse beam frequency response simulator Page: 1 of 3
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FERMI LAB-CON F-05-120-AD
A HARDWARE TRANSVERSE BEAM
FREQUENCY RESPONSE SIMULATOR*
J. Ning and C.Y Tan#, FNAL, Batavia, IL 60510, U.S.A.Abstract
We built an electronic instrument that can mimic the
transverse beam frequency response. The instrument
consists of 1) a time delay circuit with an analog-to-
digital converter (ADC) which contains a first-in-first-out
random assess memory (FIFO RAM) and a digital-to-
analog converter (DAC); 2) a variable phase shifter
circuit which is based on an all pass filter with a
bandwidth of 25kHz to 30kHz and 3) a commutating filter
which is a nonlinear band pass filter. With this
instrument, we can dynamically adjust the betatron tune,
the synchrotron tune, and the chromaticity. Using this
instrument, we are able to test other beam systems
without using actual beam.
INTRODUCTION
The Tevatron is an operational machine with limited
time for machine studies. In order to save precious study
time to test projects like the Tevatron transverse narrow
band damper system and the phase locked loop tune
tracker system, we built an instrument which simulates
the Tevatron transverse beam frequency response. This
instrument has a frequency response that is close to the
measured Tevatron transverse beam frequency response
(see Figure 1).
Date: 04-03-03 Time: 08:18 PlTRACE A: Freq Response
A Marker
-10
dB
Log~ag2
I V-60
dB
Center: 28.03 kHz
TRACE B: F2 FRESK2
B Marker
1501,Ph
d28 030.0 Hz
II I
28 030.0 Hz
-93.273 dB
IASpan: 1 kHz
-20.732 degd 1 g r 1 1 r 1 1
30
'I '-150
Center: 28.03 kHz Span: 1 kHz
Figure 1. The measured Tevatron transverse beam
frequency response.
There are three important parameters in the frequency
response. The measured center frequency which is the
betatron tune (28.030 kHz in Figure 1); the frequency
*Work supported by the US-LARP collaboration and by the
Universities Research Association Inc. under Contract No. DE-AC02-
76CH03000 with the United States Department of Energy.
cytangfnal.govdistance between the peaks of the magnitude response,
which is the synchrotron tune (~84Hz in Figure 1) and the
envelope of the magnitude response which comes from
chromaticity.
This electronic black box is used to mimic the
measured frequency response shown in Figure 1. Also,
the simulator is able to dynamically change the three
parameters of the frequency response discussed above.
THE SOLUTION
Our approach in the design of the black box design is
shown in Figure 2 and can be described as follows:
* Commutating filter. The filter's frequency response
looks like that of coasting beam, which is without
synchrotron sidebands.
* Time delay element. This is in the feedback loop to
create the synchrotron sidebands in the frequency
response of the commutating filter.
* Phase shifter. This is in the feedback loop to
smoothly shift the synchrotron sidebands.
Flier In Flter Out
Commutatnmg Fiter
A Phase Shufter Tune DelayFigure 2. The block diagram of the hardware transverse
beam frequency response simulator.A commutating filter is an RC low pass filter with
several grounded capacitors [2]. A switch sequentially
swaps one capacitor to another (see Figure 3).
^^^AFigure 3. The commutating filter
Commutating Filter
lif r
IF T T
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Ning, J. & Tan, C. Y. A Hardware transverse beam frequency response simulator, article, May 1, 2005; Batavia, Illinois. (https://digital.library.unt.edu/ark:/67531/metadc1407703/m1/1/: accessed June 11, 2024), University of North Texas Libraries, UNT Digital Library, https://digital.library.unt.edu; crediting UNT Libraries Government Documents Department.