LCLS Undulator Systems Beam Loss Monitor

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LCLS Undulator SystemsBeam Loss Monitor

• William Berg ANL/APS Diagnostics Group

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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.
• ANL Budget MS (325k detector, ctls interface
  box 100k).
• Detector Schedule (design nov-dec,drawings
  dec-feb,pro/fab/assy feb-jun,del july, inst
  aug-sep).
• Organization 4 groups, Group Definition
  (controls, detector, simulation, test
  calibration).
• Design Highlights and System Overview (detectors
  dynamic 33, static 2, rd fiber1).
• Detector design details and focus topics.
• Funds are limited and efforts need to be focused
  to minimize costs (h-dn).

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BLM Purpose h-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. BLM 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
  of 106 ) and much more sophisticated diagnostics
  hard and software.

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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.Beam Current threshold
  determination?
• 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.

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ANL Draft BLM Budget

• 425k MS Total
• 325k Detector Development
• detectors
• mounting and slide systems
• cables and fiber
• 100k Controls Interface Box

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Draft schedule
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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
Detector Group Lead W. Berg
Simulations and analysis Group Lead J. Dooling
Testing and Calibration Group
Lead B. Yang
W. Berg J. Bailey J. Dooling L. Moog
L. Emery M. Santana J. Vollaire B. Yang
A. Brill L. Erwin R. Keithley J. Morgan
M. Brown R. Diviero J. Dusatko S. Norum A.
Pietryla
Slac employee
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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 MPS Integration and User Displays.
• Detector Group W. Berg
• Develop Detector and Machine Integration.
• Simulations and Analysis Group J. Dooling
• Provide collaborative blm simulation support and
  test analysis.
• Test and Calibration Group B. Yang
• Provide beam based hardware testing programs and
  calibration plan.

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System Design Highlights

• 33 distributed detectors (one preceding each
  undulator segment), two static units (up and
  downstream of undulator hall). One additional
  channel reserved for rd fiber based system.
• MPS threshold detection and beam rate limiting.
• Single pulse detection and mps action up to max
  120Hz beam rep rate via dedicated mps link.
• Monitoring of real time shot to shot signal
  levels and record integrated values up to one
  second.
• 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 (600-1200V).
• Calibrated using upstream reference foil (initial
  use cal will be determined from simulation
  studies).

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Detector Design Highlights

• Cerenkov Radiation Based (x-ray beam noise
  immunity).
• Employs PMT for high sensitivity to beam losses.
• Dynamic detector (tracks with undulator) 100mm
  stroke. Undulator position (in/out) detection
  will be used to set the corresponding mps
  threshold levels.
• Manual static insertion option via detachable arm
  for special calibration and monitoring.
• Large area sensor (coverage of the full
  horizontal width of the top and bottom magnet
  blocks).
• Fiber Out for low gain upgrade (full integration
  and dyn range diagnostic), control system
  expandable to 80 channels.
• Radiation hard components (materials and
  electronics).

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BLM Interconnect Diagram m. brown
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Interface Box Location
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Plan View of Short Drift
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BFW Pump Out Port Relocation
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Removable Pin for Manual Insertion
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Undulator Inserted Position
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Undulator Retracted Position
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Pin Function
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Detector Pin Detail
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Rendering of Detector
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• Cross Section of BLM Detector

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Cerenkov Radiator
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Magnet Block Sensor Coverage
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Proposed PMT Device -04 (420nm)
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Vendor List

• Radiator Substrate water jet and final polish
  (lap and flame) (quartz)- VA Optical
• Radiator AlSi coating Eddy Company
• Radiator Material - Corning
• PMT and Magnetic Shield - Hamamatsu
• Connectors
• SMA Fiber Feed through) -Thor Labs
• High Voltage Feed through - Kings
• SMB Signal Fed through - AMP
• Fiber Optic Cable (heartbeat) Fiber (fused
  silica) - Stocker Yale
• Fiber Optics Cable, UV Grade Coastal
  Connections
• Signal Cable Belden
• Body Fabrication- M1, High Tech, AJR Industries
• Miscellaneous Hardware (fasteners, o-rings, flex
  coupling, spanner wrench) McMaster-Carr
• Linear Bearing Assembly IKO International
• Spherical Bearing Aurora Bearing

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UV Grade Fiber
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Fused Silica Radiator
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BLM System Support Focus Topics

• Funding of beam based prototyping and test
  program.
• Implementation of upstream calibration foil (alt.
  profile monitor/halo).
• BFW prototype tolerance verification (system
  tolerance in LTT)

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BLM Summary

• Undulator magnets protection is critical for
  machine commissioning period.
• BLM system is now defined as a component of the
  mps (descope) with an upgrade path to a
  diagnostic (low gain detector).
• Calibration plan and hardware is vital to proper
  system operation (threshold detection will use
  empirically derived levels).
• Schedule for development of the blm program is
  very aggressive and funding is limited.

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Detector Summary

• Building a detector based on cerenkov radiation
  and PMT detection.
• 36 distributed channels (2 static devices)
  capable of single pulse detection (up to full rep
  rate) with rate limiting reaction.
• Detectors dynamically track with undulator
  position with manual detach option to remain in a
  fully inserted static position.
• Adjustable PMT sensitivity with remotely
  controlled high voltage power supply.
• Keep alive system test (led pulser) before each
  beam pulse.
• All Vendors have been identified, Quotes in
  progress, Drawing set being reviewed.
• Installation does not require access into the
  vacuum system or removal of other components.

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• End of Presentation

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Parts Animation
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Undulator System
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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).
• BFW prototype verification (system tolerance LTT)

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Summary

• Undulator magnets protection is critical for
  machine commissioning period.
• Schedule for development of the blm program 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 detector).
• 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 will use
  empirically derived levels).
• Quotes in progress
• Drawing set being reviewed

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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 detector interface box (pmt, led pulser, sig
  con?) 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 from 8 to16
  channels).

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Undulator Hardware
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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

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Segment Design Layout m. brown
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Locking Pin Detail
(moves with undulator)
Flex Joint
Spherical Bearing
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Beam Loss Monitors using Link Nodes
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Beam Loss Monitor - Undulator Hardware (m. brown)
In Undulator Hall
Long Haul Cables
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Proposed PIC / BLM Timing
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Link Node Block Diagram
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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

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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

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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

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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

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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.

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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

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BLM Controls Architecture

• 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 (? verify this number) link node
  chasses serving up to 8 BLMs along the undulator
  (a diagram would help here)

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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

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MPS Overview (m. brown)
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System Roll