LER BBA: QUAD Shunt History

1
LER BBA Quad Shunt Project
Marc Ross Doug McCormick Justin May Janice
Nelson Jerry Yocky Nicole Varela Juan Cruz Tonee
Smith
2
LER BBA Retrospective

• Last fall a BBA program was initiated in both
  PEP-II rings as part of a larger effort to
  further understand the BPM performance.
• HER results were successfully implemented, and
  served to validate the BBA procedure.
• LER results have also been implemented, but not
  fully utilized.
• Reanalysis of results with fully coupled
  algorithm was needed.
• IR2 results (the most important) have been
  limited by lack of independent quadrupole control

3
LER BBA Program goals

• To find the magnetic center of quadrupoles at
  optically sensitive locations in the ring.
  Shunts are used to vary the field in one magnet
  which otherwise lacks individual control.
• In IR2, there are four strings powering a total
  of 14 quads QFCY1 (4), QDCY2 (4), QFCX3 (2),
  QDCX2 (4)
• Throughout the ring there are 37 individual QD
  and QF (tune) quads which have been identified as
  prime candidates for BBA.
• These are in the arcs, immediately adjacent to
  sextupoles
• There are 2-5 quads per half-arc

4
LER BBA Quad Shunt History

• In 1995, switchable shunt resistor circuits were
  installed on each quadrupole in the SPEAR ring to
  facilitate beam-based alignment. They were used
  with great success.
• These shunts were removed as part of the SPEAR3
  upgrade, and the hardware was sent to Salvage.
• The shunts were moved to B15 and proposals were
  made to upgrade them for use in PEP-II (all
  ultimately deemed too costly) .
• The shunts were taken as is to NLCTA, cleaned up,
  and tested on a LER Quad in Magnetic
  Measurements. 42/45 were found to be fully
  functional.

5
LER BBA Quad shunt hardware

• The shunts consist of two high-power (250W)
  resistors in parallel on a 1 copper heat sink,
  controlled by an IDOM-driven FET switch.

6
LER BBA Shunt Hardware details

• Water cooling unnecessary for our application
  (resistors operating at 15 rated power on a
  large thermal mass).
• We have tested at 150 expected operating power
  for 1 hour. Max temperature reached was 55ºC
  without water cooling.
• Design is simple yet robust, with a low mortality
  rate even after months outside in Salvage.
• Minor control board modifications (snubber
  circuit) were made to protect the FET switches at
  our operating values.
• No-frills controls (24V, on/off, and
  minimally-calibrated analog read back of shunt
  current) allowed for a straightforward cable
  plant.

7
LER BBA Quad shunt installation

• We currently have 18 shunts installed on
  individual QD and QF magnets throughout the ring.
• High power resistor values 0.45 W and 0.55 W will
  shunt 3 of an individual QD or QF magnets
  current
• These have been checked out on the bench (dummy
  load and test stand magnet) and in the field (SCP
  control) and are ready for BBA when PEP turns on
  next year.

String   Magnet R Mag I Mag V Shunt V Shunt R Shunt I Shunt  Shunt P
QD(18) 0.019 300 5.7 4.2 0.45 9.3 3.11 39.2
  0.019 300 5.7 4.2 0.55 7.6 2.55 32.1
QF(19) 0.019 300 5.7 4.2 0.45 9.3 3.11 39.2
  0.019 300 5.7 4.2 0.55 7.6 2.55 32.1
8
LER BBA Quad shunt inventory

• We have 8 of the IR2 shunts completed, three were
  installed before the safety stand-down.
• Resistors available off-the-shelf (18 W, giving 9
  W shunts with two in parallel) will shunt 1.8-1.9
  magnet current.
• Resistors for the remaining 6 boards are on
  order, we expect delivery this week.
• These will also be 9 W shunts.
• Boards are ready, just awaiting resistor
  delivery.
• Cable plant is in place. Final checkout SCP ?
  Shunt required.

9
LER BBA IR2 Quad Shunts
String   Magnet R Mag I Mag V Shunt V Shunt R Shunt I Shunt  Shunt P
QFCY1.1 0.18 70 12.8 11.3 9 1.3 1.79 14.1
1.2 0.18 70 12.8 11.3 9 1.3 1.79 14.1
1.3 0.18 70 12.8 11.3 9 1.3 1.79 14.1
1.4 0.18 70 12.8 11.3 9 1.3 1.79 14.1
QDCY2.1 0.18 106 19.3 17.8 9 2.0 1.87 35.3
2.2 0.18 106 19.3 17.8 9 2.0 1.87 35.3
2.3 0.18 106 19.3 17.8 9 2.0 1.87 35.3
2.4 0.18 106 19.3 17.8 9 2.0 1.87 35.3
QFCX3.1 0.18 140 25.6 24.1 9 2.7 1.91 64.3
3.2 0.18 140 25.6 24.1 9 2.7 1.91 64.3
QDCX2.1 0.18 147 26.7 25.2 9 2.8 1.91 70.6
2.2 0.18 147 26.7 25.2 9 2.8 1.91 70.6
2.3 0.18 147 26.7 25.2 9 2.8 1.91 70.6
2.4 0.18 147 26.7 25.2 9 2.8 1.91 70.6
10
Quad shunt installation, QD/QF

• We have installed 1-2 moveable shunts per
  half-arc (2-4 shunts per IR/micro), based on
  quad(/sext) population.
• The shunts hook directly across the busses of a
  quad with leads that bear an uncanny resemblance
  to automotive jumper cables.
• Shunt blocks/enclosures are grounded to the PEP
  magnet rafts.
• After a round of BBA, these shunts will be moved
  at the next opportunity to a neighboring
  candidate QD or QF.
• Lather, rinse, repeat. (Two RODs to complete the
  QD/QF magnets)

11
Quad shunt installation, IR2

• We are planning to complete installation of one
  shunt on each of the 14 QF/DCX/Y quads in IR2.
• The shunts also hook directly across the busses
  of the quads, but will not be moved from magnet
  to magnet.
• Modifications to the shunt covers have been made
  to prevent contact with electrical hazards
  within.
• IR2 magnets are not PPS-interlocked, and the
  shunts are not contained within existing magnet
  covers.
• We are prepared to install the eight we have
  pending work approval, the remaining six as soon
  as theyre ready.

12
Quad shunt controls

• To the control system, the shunts look like
  generic digital devices with a corresponding
  analog readback.
• Moveable shunts have names like PR04 SHUNT1, 2,
  3
• One digital control (IDOM bit) per shunt (command
  ON/OFF)
• One status (ON/OFF) reflecting that IDOM bit
• One ASTS value reflecting current through the
  shunt resistors
• Not presently calibrated well enough to tell more
  than whether the shunt is shunting or not,
  really.
• Weve requested that the shunt on/off status be
  on the SDS CUD under LGPS with ON being RED.

13
SCP Panel Analog display
14
How it all works

• We are creating a flat file to hold the
  information of which shunt is on which quad, with
  a list at the bottom of which shunts can go to
  which quads.
• This file will live on the VAX with an entry in
  e-log (which e-log to be determined) with its
  location.
• The person who physically moves the shunts to new
  magnets is required to change this file.
• For data acquisition, a button macro will prompt
  which magnet or which shunt you wish to do BBA
  on, then load up a CRR and take data.
• Data to be analyzed offline by the Woodley/Wolski
  coupled analysis matlab code.