RHIC 10 Hz global orbit feedback system Page: 4 of 5
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turns, and send the 8-turn average to the ML-510
processing modules located in the 6 service buildings.
" Power supply control PLC -
ML-510 processing module
Module Kepco power
I nn I
'fl e r* tcj
)rr ~- cr
Figure 3: Typical equipment rack layout (1012A)
showing BPM modules with Ethernet connection for
BPM position data distribution, power supply control
PLC panel, Kepco power supplies, and Xilinx Virtex-5
ML-510 processing and analog output module.
Sgna i nputs
Frewireto VME DAC for
BemSycLikSeocm card BPM odaa Mr 0b~o ocal
Figure 4: RHIC BPM hardware board with daughter card.
Figure 5: Control loop filter response.
BPM Data Distribution Network 
The standard Ethernet low level packet structure was
selected for distributing BPM data in order to allow off-
the-shelf network switch hardware to be used. After
evaluation of several network switches, Netgear models
GS724AT (24 RJ-45 connections, with 4 SFP ports) and
GSM7212 (12 SFP ports) 1 gigabit switches were selected
for their low latency performance (-2 microseconds).
The BPM daughter cards connect to the local network
switch via RJ-45 CAT-6 cables, and fiber optic cables are
used to interconnect the network switches between
alcoves and service buildings (Fig. 1). The service
buildings are interconnected in a star configuration
through a main hub room in building 1005S.
The software/firmware block diagram for the ML-510
processing module is provided in figure 2. The on-board
Xilinx Virtex-5 has a dual core Power PC 440, one of
which is running the vxWorks real-time operating system
and RHIC accelerator device object (ADO) software for
interfacing with the higher level control system via the
controls Ethernet network. The other Power PC is
unused. The remaining software blocks shown in the
diagram are implemented in VHDL gate array code.
Each ML-510 generates setpoints for 4 local magnet
power supplies (2 per ring). A 36 x 1 matrix calculations
is performed every 103 microseconds to calculate each
power supply setpoint using up to 36 BPM measurements
per ring. The SVD matrix output value  is processed
by the control loop filter with the frequency and phase
response shown in Fig. 5. This filter has proven very
effective in correcting frequencies around 10 Hz while
ignoring slow orbit shifts as occur during application of
slow orbit feedback  and actions such as removal of
separation bumps to bring beams into collision.
The corrector magnet power supply setpoints are
generated by an AD475R +/-10V 16-bit DAC (Fig. 6).
SMA connectors interface to the Kepco power supplies.
Corrector Magnets 
Each magnet coil pair is wired in parallel, and in series
with a 7-turn reverse coil installed on the magnet in the
other ring. The reverse coil is used to counteract the
fringe field affects on the other beam. Figures 7 and 8
show a typical magnet installation in the RHIC tunnel.
Twenty four magnets are installed in total, 12 in each
ring, and are located near each of the triplet magnets that
are driving the 10 Hz perturbations.
Figure 6: ML-510 processing module with DAC card.
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Michnoff, R.; Arnold, L.; Carboni, L.; Cerniglia, P; Curcio, A.; DeSanto, L. et al. RHIC 10 Hz global orbit feedback system, article, March 28, 2011; United States. (digital.library.unt.edu/ark:/67531/metadc831394/m1/4/: accessed December 16, 2018), University of North Texas Libraries, Digital Library, digital.library.unt.edu; crediting UNT Libraries Government Documents Department.