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LER BBA: QUAD Shunt History

LER BBA: QUAD Shunt History. In 1995, switchable shunt resistor circuits were installed on each quadrupole in the SPEAR ring to facilitate BBA. They were used with great success. These shunts were removed as part of the SPEAR3 upgrade, and the hardware was sent to Salvage.

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LER BBA: QUAD Shunt History

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  1. LER BBA: QUAD Shunt History • In 1995, switchable shunt resistor circuits were installed on each quadrupole in the SPEAR ring to facilitate BBA. 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 (expensive) proposals were made to upgrade them for use in PEP2. • 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.

  2. LER BBA: Quad shunt hardware • The shunts consist of two high-power resistors in parallel on a 1” copper heat sink, controlled by a basic IDOM-driven FET switch. • 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. • Each shunt will be tested at operating current/voltage before installation. • Design is simple yet robust, with a low mortality rate even after months outside in Salvage. • Minor control board modifications (snubber circuit rework) are being made to protect the FET switches at our operating values. • No-frills controls (+24V, on/off, and as-yet-uncalibrated analog readback of shunt current) make for straightforward cable runs.

  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 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 inventory • We currently have 18 shunts suitable for use on individual QD and QF magnets. • High power resistor values 0.45 W and 0.55 W will shunt 3-4% of a QD/QF magnet’s current. • We are expecting delivery of resistors for 8 of the IR2 shunts this week. • Available resistors (9 W) will shunt 1-2% magnet current. • Resistors for the remaining 6 boards are on order, we expect delivery in December. • These will also be 9 W.

  5. Quad shunt installation, QD/QF • We are installing 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. • Design to be approved. • Control cables have been pulled everywhere but IR2. • After a round of BBA, these shunts will be moved (during a ROD, presumably) to a neighboring candidate QD or QF. • Lather, rinse, repeat. (Two RODs to complete the QD/QF magnets)

  6. Quad shunt installation, IR2 • We are planning to install one non-moveable shunt on each of the 14 QF/DCX/Yn quads in IR2. • The shunts also hook directly across the busses of the quads, but with a more captive ring-clamp fixture. • Modifications to the shunt covers will have to be made to keep fingers out (quads are not PPS interlocked). • We hope to install eight of these before turn-on. • The remaining six will go in this December (or over the break). • We are planning to have all the cables pulled this downtime, but some may carry over into December if we run out of cable.

  7. Quad shunt controls • To the control system, the shunts will look like generic digital devices with a corresponding analog readback. • With 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. • SCP Panel and analog status display group exist, though not linked to a PEP panel yet. • We’ve requested that the shunt on/off status be on the SDS CUD under LGPS with ON being RED.

  8. SCP Panel & Analog display

  9. 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 somewhere with an entry in e-log (which e-log to be determined) with its location. • The person who moved the shunts 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.

  10. The Crew • The project has been brought to you by the usual suspects: • Marc Ross, Doug McCormick, Tonee Smith, Justin May, Janice Nelson, Nicole Varela, Juan Cruz • with the invaluable input of Those Who Know: • Paul Bellomo, Jerry Yocky, Bob Fuller, Nancy Spencer, Mario Ortega, Mark Woodley

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