Dec. 14, 2004PEP-II MAC Tonee Smith, ILC 1 LER BBA Quad Shunt Project Marc Ross Doug McCormick Justin May Janice Nelson Jerry Yocky Nicole Varela Juan Cruz Tonee Smith

Dec. 14, 2004PEP-II MAC Tonee Smith, ILC 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

Dec. 14, 2004PEP-II MAC Tonee Smith, ILC 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

Dec. 14, 2004PEP-II MAC Tonee Smith, ILC 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.

Dec. 14, 2004PEP-II MAC Tonee Smith, ILC 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.

Dec. 14, 2004PEP-II MAC Tonee Smith, ILC 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.

Dec. 14, 2004PEP-II MAC Tonee Smith, ILC 7 String Magnet RMag IMag VShunt VShunt RShunt IShunt % Shunt P QD(18) QF(19) We currently have 18 shunts installed on individual QD and QF magnets throughout the ring. High power resistor values 0.45  and 0.55  will shunt ~3% of an individual QD or QF magnet’s 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. LER BBA: Quad shunt installation

Dec. 14, 2004PEP-II MAC Tonee Smith, ILC 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  giving  shunts with two in parallel) will shunt % magnet current. Resistors for the remaining 6 boards are on order, we expect delivery this week. These will also be 9  shunts. Boards are ready, just awaiting resistor delivery. Cable plant is in place. Final checkout SCP  Shunt required.

Dec. 14, 2004PEP-II MAC Tonee Smith, ILC 9 String Magnet RMag IMag VShunt VShunt RShunt IShunt % Shunt P QFCY QDCY QFCX QDCX LER BBA: IR2 Quad Shunts

Dec. 14, 2004PEP-II MAC Tonee Smith, ILC 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)

Dec. 14, 2004PEP-II MAC Tonee Smith, ILC 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 they’re ready.

Dec. 14, 2004PEP-II MAC Tonee Smith, ILC 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. –We’ve requested that the shunt on/off status be on the SDS CUD under LGPS with ON being RED.

Dec. 14, 2004PEP-II MAC Tonee Smith, ILC 13 SCP Panel & Analog display

Dec. 14, 2004PEP-II MAC Tonee Smith, ILC 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.