BNL Collider Complex Overview. MPS at the collider accelerator department (C-AD) RHIC Accelerator Protection Elements

Transcription

1 MPS Experience at BNL-RHIC BNL Collider Complex Overview MPS at the collider accelerator department (C-AD) RHIC Accelerator Protection Elements Operational Experience Summary

2 BNL Collider Complex Overview

3 BNL Collider Complex Overview MPS at C-AD RHIC Accelerator Protection Elements Operational Experience Summary

4 MPS at C-AD The Machine Protection Systems at BNL are very mature. Conception and implementation for the pre-injectors was established long ago, before the RHIC-era. The RHIC MPS was designed in the 1990 s and leveraged strongly off the experiences from FNAL. This talk will present the machine protections systems of the presently operating accelerator facilities at C-AD. The Machine Protection System at BNL consists of three parts: 1) input measurements (and subsystem interlock systems) 2) beam interlock system ( permit system ) 3) consequences: mechanisms for preventing beam into regions of interest (injectors) or dumping the beams (in RHIC)

5 Presently there are 5 permit links (which are not interdependent) and a stand-alone MPS for the linac. RHIC EBIS LINAC Booster NSRL AGS AGS-to-RHIC transport (AtR) Permit Link Function #1 Booster prevent beam in the NSRL line / acceleration in Booster #2 AGS prevent accelerating beam in the AGS #3 AtR (U/V/W) prevent beam from entering the AtR line #4 Arc prevent beam from entering RHIC #5 RHIC eliminate circulating beam in RHIC These protect the accelerators from damage due to the beam. At RHIC, the superconducting magnets are also protected from the release of stored energy by quench protection links.

6 12 MV LINAC 200 MeV LINAC Booster MPS prevents beam in the NSRL line and acceleration in the Booster R-Line NSRL (NASA Space Radiation laboratory) BOOSTER ~ 1 GeV/A Au ~ 2.3 GeV pol protons AGS EBIS He to Au ~ 2 ma H- 50 ma (polarized) protons 1 na

7 Booster MPS input measurements condition for beam inhibit vacuum valves (R-line) vacuum valves* (Booster) power supply status (R-line) PLCs valves closed valves closed on/off status fault dose on NSRL target sample (measured using ion chambers) desired dose achieved consequences booster RF drive signal set to zero R-Line extraction bumps inhibited main magnet power supply ramped up to spiral beam into dump * (reachback to chopper in linac fast-beam inhibit system) The Booster permit link system also allows for inhibiting beam to R-Line while allowing beam in Booster for other Booster-users (e.g. AGS and/or other Booster beam development)

8 Booster Permit Link configuration and status example operator level readbacks link monitoring status inputs status of inputs input enable/disable

9 AGS MPS prevents accelerating beam in the AGS BOOSTER ~ 1 GeV/A Au ~ 2.3 GeV pol protons BtA AGS ~ 10 GeV/A Au ~ 24 GeV pol protons input measurements vacuum valves loss monitor manager loss monitors at sensitive locations magnet ( snake ) quench detector dump bump power supply status beam current transformer (2 units) transformer keep-alive statuses condition for beam inhibit valve closed beam loss exceeds threshold beam loss exceeds threshold quench event on/off status fault beam current exceeds threshold (and AtR dipoles on) status fault consequences AGS RF drive signal set to zero extraction bumps inhibited if operating with polarized protons, source is inhibited

10 ARC MPS prevents beam from entering RHIC RHIC ~ 100 GeV/A Au ~ 250 GeV pol protons input measurements vacuum valves RHIC permits to the arc condition for beam inhibit valve closed fault Blue magnet quench detector Yellow magnet quench detector consequences quench event quench event switching magnet turned off U/V/W (Accelerator to RHIC) MPS prevents beam from entering the AtR line AGS ~ 10 GeV/A Au ~ 24 GeV pol protons input measurements vacuum valves PASS (aka PPS) status, division A PASS status, division B condition for beam inhibit valve closed access control state not in no access consequences extraction kicker triggers from AGS disabled

11 RHIC MPS eliminates circulating beam in RHIC RHIC ~ 100 GeV/A Au ~ 250 GeV pol protons input measurements condition for beam inhibit loss monitors vacuum valves power supply status PLCs beam loss exceeds threshold valve closed on/off status fault roman pot positions (both rings) beam loss at roman pots RF cavity voltage PASS (aka PPS) status, division A PASS status, division B PASS Beam Stop status (A and B) Blue magnet quench detector Yellow magnet quench detector quench detector (snakes and rotators) position error beam loss exceeds threshold voltage status fault access controls state not in no access quench event quench event quench event consequences RHIC abort kickers triggered

12 BNL Collider Complex Overview MPS at C-AD RHIC Accelerator Protection Elements Operational Experience Summary

13 RHIC Accelerator Protection Elements Equipment monitoring systems Beam monitoring systems Beam interlock system ( permit system ) Beam dumping system (collimation and gap cleaning primarily for detector backgrounds) Equipment monitoring systems Conventional: vacuum valves, vacuum pump status, power supply outputs, RHIC specific: superconducting magnet quench protection system

14 RHIC superconducting magnet quench protection system consists of quench detectors quench protection assembly (and interface chasses) quench protection switches quench link (one link per ring) one QD in every arc s center alcove monitoring voltage taps in the arcs two QDs in service buildings monitoring magnet and lead voltage taps in the insertion regions voltage readout at 720 Hz

15 Beam monitoring systems: beam loss monitors (BLM) For MPS: ~ 430 gas ionization chambers (RHIC) ~ 100 in AGS to RHIC transfer line based on Tevatron design (R. Shafer) BLM data handling, two paths: (1) to MADCs (1 Hz averaged data for logging, 720 Hz for post mortem analyses) (2) to pair of threshold detectors (comparators) for detection of slow losses (time constant ~ 20 ms) fast losses (time constant ~ 100 ms) which produce an inhibit if threshold is exceeded Other beam loss diagnostics: pin diodes (Bergoz) photomultiplier tubes (JLAB-CEBAF design)

16 Beam monitoring systems: beam current monitors Pair (for redundancy) of back-to-back Bergoz NPCTs with internal keep-alive circuit (constant 15 ma rms / 65 mv rms, khz signal). Fault produced if current exceeds threshold or if keep-alive current not measured. assembly in shop as installed in the AGS Plan for ERL: pair of Bergoz New Parametric Current Transformers (NPCT) for differential beam loss measurement

17 Beam interlock system consists of 10 MHz carrier(s) 3 permit links (2 for QDs, 1 for all else) 32 beam interlock controllers (BIC) up to 192 distributed user system inputs 1 dedicated master to initiate establishment of a permit Full system tests on demand (typically during startup) Max response time (permit failure to abort) ~ 40 microseconds or ~ 3.2 turns BIC, conceptual view BIC FEC list QD link inputs

18 Beam dumping system consists of kicker magnets pulse forming networks (PFNs) dump absorber design assumptions: E max = 200 kj at 100 GeV/A with N b =60, N ppb =1E9 (Au) concern: secondary particle emission from dump absorber could heat and quench downstream superconducting magnets response time: charging supply for PFN disconnect ~ 10 ms (~ 1 turn) trigger synchronization (~ 1 turn) (plus transit time from permit link ~ 3 turns 5 turns total or 60 ms) RHIC blue dump kicker assemblies RHIC blue beam dump

19 BNL Collider Complex Overview MPS at C-AD RHIC Accelerator Protection Elements Operational Experience Summary

20 Operational Experience The well-established C-AD MPS system generally works as expected. There may be more permit pulls than necessary, but not excessively so. Failures of the MPS concern dynamics either not considered in the MPS design or result from operation with beam intensities higher than envisioned in the MPS design. These lessons learned will be reviewed next.

21 AGS beam-induced vacuum failures (2008) Issue Remedies operation with 4 Au bunches, 5E9 ppb resulted in 3 vacuum leaks dump bump amplitude increased dump moved closer to beam plunging stripping foil implemented motivation: force Au ions to lose 2 remaining electrons in 1 mil Tungsten foil resulting in beam rigidity decrease and hence larger deflection due to dump bump AGS beam dump AGS plunging stripping foil Recent issue (2014): MPS designed to inhibit beam to downstream systems but not to protect the accelerator from itself (plethora of spurious BLM readings causing beam inward spiral during acceleration due to rf turn-off strategy)

22 RHIC quenches due to beam aborts (2010) Issue Remedies beam aborts at high energy caused quenching of magnets downstream of dump additional BLMs installed (subsequently determined desire for less sensitive BLMs avoiding saturation during an abort as potentially useful in understanding beam abort dynamics) additional absorbers (20 5-inch sleeves) installed in the RHIC beam pipe adjacent to the dump to increase wall thickness no abort-induced quenches in following year of operations simulations: no quenches for up to 2.5E11 ppb (250 GeV protons) dump shielding sleeve

23 RHIC quenches due to beam aborts (2013) Issue Observations quenches caused by beam abort measured abort kicker currents different (during operations and maintenance days) measured abort kicker currents does not track with new fast-sampled beam position measurements Diagnosis Remedies inductance of ferrites changes with beam-induced temperature rise actively being investigated plan for major abort kicker upgrades in summer, 2014

24 RHIC abort kicker pre-fires (up to and including 2013) Issue damage to experiment s detectors (STAR in particular) Remedy run 14 move beam towards aperture so that prefire deposits beam upstream Remedy > run 14 installation of dedicated collimator(s)

25 Summary The RHIC physics program entails a very wide variety of particle species and energies The MPS design for the C-AD preinjectors is mature, maybe rudimentary by today s standards, but robust Ever-increasing beam intensities required by the evolving requirements of the physics programs have motivated and continue to motivate MPS sub-system upgrades A new era of MPS systems is under development at C-AD for (electron-based) new projects including electron lenses, conventional electron cooling, coherent electron cooling (new), and the energy recovery linac project

26 Acknowledgements (for this presentation) For MPS as seen by Operations throughout the accelerator complex: Travis Shrey For user-distributed inputs: general: Travis Shrey and Greg Marr (Operations) + Loralie Smart (Vacuum) + John Butler (RF) + Don Bruno (Power Supplies, Quench Detection) + David Gassner, Peter Oddo, Michelle Wilinski (Beam Instrumentation) For beam permit system: Kevin Brown, Peter Ingrassia, Travis Shrey, Charles Theisen For RHIC beam dump: RHIC Configuration Manual (2006) For operational experience: AGS vacuum issues Leif Ahrens RHIC quenches due to beam aborts, 2010 Christoph Montag RHIC quenches due to beam aborts, 2013 Rob Hulsart, Rob Michnoff, Peter Thieberger RHIC abort kicker prefires, 2013 Angelika Drees, Christoph Montag, Rob Hulsart, Aljosa Marusic, Rob Michnoff, Peter Thieberger, Simon White For photographs: Don Bruno, Dave Gassner, Paul Sampson, Joe Tuozzolo

27 Current and Future Developments in Controls A stand-along MPS system for the Electron Beam Ion Source (EBIS), called EGIS, was developed by Omar Gould MPS designs for future projects Energy Recovery Linac (ERL) electron lens new 56 MHz SC cavity for RHIC Coherent Electron Cooling are being developed using NI CompactRIO platforms The Controls portion of the MPS for these systems is being developed by: Zeynep Altinbas, Mike Costanzo, Chung Ho and Charles Theisen (systems design and permit link boards) Jim Jamilkowski, and Prerana Kankiya (ADO manager interfaces) Peggy Harvey (MPS interfaces to rf systems) Prachi Chitnis (student, reliability analysis) Also under development is a stand-alone quench detection system for the ERL superconducting solenoids (using NI PXIe platform)

28 Quench protection in RHIC spare slides

29 Preparation for higher beam intensities: beam position monitors Issue The cold BPM cables (those located in the insulating vacuum) consist of a stainless steel outer conductor with a tefzel dielectric. If the beam-induced power is too large, this dielectric will melt. achieved bunch length limitation by cryogenic system nominal intensity intensity after upgrades BPM excursion monitor developed based on absolute BPM measurements (striplines)