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LCLS Undulator Systems Beam Loss Monitor Control Interface. Josh Stein LCLS Undulator Controls CAM/TL Bill Berg ANL/APS Diagnostics Group Arturo Alarcon SLAC Controls. Undulator Protection Requirements. Inputs to inhibit the e-beam
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LCLS Undulator SystemsBeam Loss Monitor Control Interface Josh Stein LCLS Undulator Controls CAM/TL Bill Berg ANL/APS Diagnostics Group Arturo Alarcon SLAC Controls
Undulator Protection Requirements • Inputs to inhibit the e-beam • Primary protection from a number of Beam Loss Monitors (BLMs) along the undulator • Secondary protection from control system monitoring of • BPM orbit • Magnet power supply status • Magnet mover status • Long-term monitoring of the radiation dose • Dosimeters attached to the magnets
BLM Specification • A single BLM will be placed in each of the gaps between undulator modules. • Design is to maximize the sensitivity of the monitor • Located as close as possible to the beam axis as the vacuum chamber allows • Choose a sensitive Cerenkov medium coupled to a high gain photomultiplier tube • The detector will not be segmented to provide transverse position information of the losses
BLM Rolls Out with Undulator Magnet • The BLM is mounted to tightly surround the vacuum pipe near the beam finder wire • It is on a linear slide so that it can be moved off the beam when the undulator magnet is rolled out • An detachable arm makes the BLM and magnet roll out together • The BLM will automatically be less sensitive to beam loss when the undulator is in the out position • The BLM can be manually inserted on the beam pipe for special calibration procedures
BLM reliability and self test • Each loss monitor is equipped with a LED that flashes between beam pulses. • Provides a pre-beam test of the BLM system before beam is sent through the undulator • Provides a stay-alive signal for the control system to monitor the BLM system during operation
BLM dynamic range • For simplicity and cost the BLM will be optimized for maximum sensitivity • And allowed to saturate the signal if a large loss occurs • The trip threshold is still exceeded if the device saturates so the MPS will still trip and protect the undulator • Monitoring of the loss signal to integrate the dose received by the undulator will not be valid if the device saturates • However, if large losses are anticipated such as when the beam finder wires are inserted, the gain of the PMT will be reduced to prevent saturation.
BLM Signal Monitoring • The BLM has a fast, dedicated link to the MPS to shutoff the beam within 1 pulse • The local MPS link node chassis also has a ‘slow’ network connection to the control system via channel access • Allows monitoring of the BLM level at any time • Reads back and controls the PMT voltage • Controls the LED test pulse • Controls the threshold set point for MPS trips
BLM Controls Architecture pk • The BLM PMT interfaces to the MPS link node chassis. • The IO board of the MPS link node chassis provides the ADC & DAC for the PMT. • A cable interface box is the treaty point between the MPS and the undulator BLM. • There are 5 link node chasses serving up to 8 BLMs along the undulator. (expandable to 16 channels)
Beam Loss Monitors with Link Nodes • Use Link Node to • support analog I/O IndustryPack modules • provide analog readouts to control system • set threshold levels • control HV power supplies • control LED Pulser
Beam Loss Monitor - Undulator Hardware (m. brown) In Undulator Hall Long Haul Cables
Future expansion • The link node chassis can handle more than the present number of installed BLMs • During commissioning a long fiber BLM will also be tested • It is compatible with the link node chassis controls
BLM System Support Focus Topics • 1. Assignment of Eric Norum to controls design oversight and testing. • 2. Funding of beam based prototyping and test program. • 3. Group Leaders to significantly step up direct involvement in system oversight, program implementation, and schedule tracking (controls: n. arnold, diag: g. decker, lcls: g. pile, ops/analysis: m. borland). • Active participation in simulations and simulation priority from slac. • Implementation of upstream profile monitor (halo or at min. cal foil). • Adequate analysis and shielding of upstream beam dump. • Develop long term collaboration plan for the pursuit of determining magnet damage mechanisms and thresholds via empirical methods. • Determine need and priority of BLM signal integration (diagnostic).
Summary • Undulator magnets protection is critical for machine commissioning period. • Schedule for development of the blmprogram is very aggressive and Funding is limited. • System design and fabrication must go in parallel with simulation and testing program. • Consider Minimum requirements for first level implementation. Taking advantage of existing mps infrastructure. • BLM system is now defined as a component of the mps with an upgrade path to a diagnostic (low gain detection). • 36 distributed channels (2 static devices) capable of single pulse detection and rate limiting reaction. • Detectors track with undulator position with detach option for manual operation. • Calibration plan and hardware is vital to proper system operation (Threshold detection with empirically derived levels).
Introduction • Physics Requirements Document: Heinz-Dieter Nuhn 9-28-07 (prd: 1.4-005-r0 undulator beam loss monitor). • Scope Reduction: diagnostic to mps detector. • Purpose and Requirements. • Budget: M&S 500k (325 detector ctls/mps 175). • Schedule: (design: n-m, test: f-m, fab: m-j, inst: july). • Organization: 4 groups. • Group Definition: controls, detector, simulation, test & calibration. • Design Highlights and System overview (detectors: dynamic 33, static: 2, r&d fiber:1). • Detector design details and focus topics. • Funds are limited and efforts need to be focused to minimize costs (h-dn). • Simulation of losses and damage in the undulator will proceed in parallel with the present effort (pk).
BLM Purposeh-dn • The BLM will be used for two purposes: • A: Inhibit bunches following an “above-threshold” radiation event. • B: Keep track of the accumulated exposure of the magnets in each undulator. • Purpose A is of highest priority. It will be integrated into the Machine Protection System (MPS) and requires only limited dynamic range from the detectors. • Purpose B is also desirable for understanding long-term magnet damage in combination with the undulator exchange program but requires a large dynamic range for the radiation detector (order 106 ) and much more sophisticated diagnostics hard and software.
BLM requirements pk • Primary function of the BLM is to indicate to the MPS if losses exceed preset thresholds. • MPS processor will rate limit the beam according to which threshold was exceeded and what the current beam rate is. • The thresholds will be empirically determined by inserting a thin obstruction upstream of the undulator. • Simulation of losses and damage in the undulator will proceed in parallel with the present effort.
Draft Budget Breakdown • 500kM&S Total • 325k Detector Development • 25k Interface Box • 150k Control and MPS integration • 25k link node chassis • 25k long haul cables • 50k davis bacon labor • 15k ctl modules and signal conditioning electronics • 25k clean power distribution • 10k racks
LCLS MPS Beam Loss Monitor System Engineer: W. Berg Cost Account Manager: G. Pile Technical Manager: D. Walters Scientific advisor: P. Krejcik* FEL Physics: H. Nuhn* Scientific advisor: B. Yang FEL Physics: P. Emma* Controls/MPS Group Lead (ctls) : J. Stein Lead (mps): A. Alacron* Testing and Calibration Group Lead: B. Yang Detector Group Lead: W. Berg Simulations and analysis Group Lead: M. White M. Brown * R. Diviero E. Norum S. Norum * B. Laird J. Dusatko* A. Brill L. Erwin R. Keithley J. Morgan J. Dooling B. Yang W. Berg J. Bailey J. Dooling L. Moog E. Norum M. White * Slac employee
MPS Beam Loss Monitor Group Functions • Controls Group:J stein, A. Alacron Develop BLM control and mps system: • Interface Box and Control • PMT Signal conditioning • Control and user displays • Detector Group: W. Berg Develop Detector and Interface. • Simulations and Analysis Group: M. White Provide collaborative blm simulation support and test analysis. • Test and Calibration Group: B. Yang Provide beam based hardware testing programs and calibration plan.
Design Highlights • 33 distributed detectors (one preceding each undulator segment), two static units (up and downstream of undulator hall). • One additional channel reserved for r&d fiber based system. • Dynamic detector, 100mm stroke (tracks undulator) with undulator position detection (in/out) for adjusting mps threshold levels. • Large area sensor (full horizontal width of top and bottom magnet blocks). • Manual insertion option via detachable arm for special calibration and monitoring. • Fiber out for low gain upgrade (full integration and dyn range diagnostic) system expandable to 80 channels. • Calibrated using upstream reference foil (initial use of simulation based levels). • MPS threshold detection and beam rate limiting. • Heart beat led pulser for system validation before each pulse up to full rep rate (pseudo calibration). • Remote sensitivity adjust (dynamic range) by epics controlled pmt dc power supply (600-1200Vdc out). • Single pulse detection, level measurement, and mps action at max rep rate via dedicated mps link. • Radiation hard detector (materials and electronics). • Monitoring live single shot signal levels (dedicated) and recording of integrated values to one second.