Radiation Safety Aspects of LCLS-II Accelerator at SLAC Sayed - - PowerPoint PPT Presentation

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Radiation Safety Aspects of LCLS-II Accelerator at SLAC Sayed - - PowerPoint PPT Presentation

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Radiation Safety Aspects of LCLS-II Accelerator at SLAC Sayed Rokni, Johannes Bauer, Jan Blaha, James Liu, Stan Mao, Ludovic Nicolas, Mario Santana and Shanjie Xiao SLAC National Accelerator Laboratory RadSynch 2017, NSRRC, Hsinchu, Taiwan

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SLIDE 1

Radiation Safety Aspects of LCLS-II Accelerator at SLAC

Sayed Rokni, Johannes Bauer, Jan Blaha, James Liu, Stan Mao, Ludovic Nicolas, Mario Santana and Shanjie Xiao SLAC National Accelerator Laboratory

RadSynch 2017, NSRRC, Hsinchu, Taiwan April 19-21, 2017

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SLIDE 2

2

Overview

  • Introduction: LCLS-II Project
  • Radiation Protection Issues
  • Radiation Safety Systems
  • Beam Containment System
  • Summary

RadSynch 2017, NSRRC, Hsinchu, April 19-21, 2017

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SLIDE 3

61st Annual HPS Meeting, July 17-21, 2016, Spokane, WA Slide 3

LCLS-II

New Injector and New Superconducting Linac Existing Bypass Line New Transport Line Two New Undulators Repurpose Existing Experimental Stations New Cryoplant

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SLIDE 4

4

LCLS-II- SC Linac, LCLS-I Linac

RadSynch 2017, NSRRC, Hsinchu, April 19-21, 2017

HXU SXU

  • Sec. 21-30
  • Sec. 11-20

L3

LCLS-I Linac 3-17 GeV proposed FACET-II LCLS-II SCRF Linac

0.25 GeV 1.6 GeV 4.0 GeV L2 BSY

L1

GUN 750 keV

  • Thirty five 1.3 Ghz Cryomodules
  • Two 3.9 Ghz Cryomodules
  • 300 pC, 1 Mhz, 4 GeV, 1.2 MW

CM02 CM03 HCM01 HCM02

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SLIDE 5

5

LCLS-II- Undulators

RadSynch 2017, NSRRC, Hsinchu, April 19-21, 2017

HXU SXU

  • Sec. 21-30
  • Sec. 11-20

0.2-1.3 keV (<1 MHz) 0.1-20 keV* (120 Hz) L3 1-25 keV (120 Hz) 1-5 keV (<1 MHz)

LCLS-I Linac 3-17 GeV proposed FACET-II LCLS-II SCRF Linac

0.25 GeV 1.6 GeV 4.0 GeV L2 BSY

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SLIDE 6

6

Dump Hall and FEE

RadSynch 2017, NSRRC, Hsinchu, April 19-21, 2017

Electron beam dumps 2x120 kW @ 4GeV (240 kW @8 GeV) Photon stoppers

FEE NEH

HXU SXU

  • Sec. 21-30
  • Sec. 11-20

0.2-1.3 keV (<1 MHz) 0.1-20 keV* (120 Hz) L3 1-25 keV (120 Hz) 1-5 keV (<1 MHz)

LCLS-I Linac 3-17 GeV proposed FACET-II LCLS-II SCRF Linac

0.25 GeV 1.6 GeV 4.0 GeV L2 BSY

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SLIDE 7

7

LCLS-II Status

RadSynch 2017, NSRRC, Hsinchu, April 19-21, 2017

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SLIDE 8

8

LCLS-II Status

RadSynch 2017, NSRRC, Hsinchu, April 19-21, 2017

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SLIDE 9

LCLS-II Commissioning Plans

  • Early Injector Commissioning: January 2018
  • HXR Commissioning with Copper Linac: 6/12/2019
  • HXR Commissioning with SC Linac:10/3/2019
  • SXR Commissioning with SC Linac:10/3/2019
  • Power Up Ramp:11/12/2019 – 8/7/2022
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SLIDE 10

10 RadSynch 2017, NSRRC, Hsinchu, April 19-21, 2017

  • High average electron beam power, MHz rep rate machine
  • No MW dump, must rely on interlocks and distribute power in several

lines

  • Fast shut-off time is required to terminate errant beam conditions
  • Pre-existing facility
  • Beam Transport Hall, Dump Hall, FEE designed for LCLS-I
  • Over 450 penetrations from the Linac to the Klystron Gallery
  • Personnel working in experimental hutches located near zero-degree

with respect to the electron beam direction and at short distance

  • Containment of FEL
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SLIDE 11

SLAC Radiation Safety Systems

Access Control System

(keep people away from radiation)

Radiation Control System

(keep radiation away from people)

Shielding Radiation Safety System Beam Shut- Off Ion Chambers

  • Beam Parameter Monitors
  • Beam Loss Monitors

11

Protection of Safety Devices Stoppers, Collimators Beam Containment System

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SLIDE 12

12

17 mSv/h

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SLIDE 13

13

Beam Transport Hall (designed for 5 kW)

RadSynch 2017, NSRRC, Hsinchu, April 19-21, 2017

6’ (1.8 m)

Local shielding around collimators

Long detectors

  • Normal Beam Loss = 1 W/m  LION setting = 35 W

S.B. BTH

18’ (5.5 m)

  • Beam Power = 2 x 120 kW  2 x 240 kW @8 GeV
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SLIDE 14

Beam Containment: Protection Collimators

  • Tunnels and shielding implemented in FLUKA
  • Cu-Line, HXR, SXR and DML imported from MadX twiss files into

FLUKA with MadFLUKA. This includes geometry & optics

  • Optics perturbations with one independent failure in magnetic routine

14

RadSynch 2017, NSRRC, Hsinchu, April 19-21, 2017

Uncontained rays towards ESA Collimator added with optimized dimensions

Courtesy of Mario Santana

14

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SLIDE 15

Beam Containment: Protection Collimators

  • Tunnels and shielding implemented in FLUKA
  • Cu-Line, HXR, SXR and DML imported from MadX twiss files into

FLUKA with MadFLUKA. This includes geometry & optics

  • Optics perturbations with one independent failure in magnetic routine

15

RadSynch 2017, NSRRC, Hsinchu, April 19-21, 2017

15

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SLIDE 16

Containment of the Electron Beam

  • Copper beam stopper (personnel safety device: 4" in diameter 30" long -53.6 r.l.)

that was destroyed by the SLAC electron beam 500 kW, 18 GeV, (11 s for radial blow out, 49 s for burn through)

  • D. Walz et al., SLAC-PUB-1224 1973
  • The 1 MW ~ 30 micron beam can be very destructive if steered onto a

component and hazardous if sent towards walls / shielding:

  • Beam needs to be shut-off very fast

16

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SLIDE 17

17

Beam shutoff studies

RadSynch 2017, NSRRC, Hsinchu, April 19-21, 2017

  • FLUKA used to compute energy deposition in various materials and

irradiation conditions (beam energy & size, geometry, impact parameter)

  • FHeat3D heat transfer code developed to compute heat transfer:
  • Interfaced ‘directly’ with FLUKA output
  • Conduction, convection, radiation
  • Collimators (W)
  • tr > 150 μs @ 120 kW  damage
  • tr > 1 s @ 120 kW  melting
  • tr > 1 ms @ 1200 kW  melting
  • Alternatives: Ti or Al
  • 250 kW Al/Cu dump (2 cm Raster):
  • tr (cooling loss) = 15 s; tr (1.2 MW) = 1.5 s; tr (raster failure) = 1.5 s

Courtesy of Mario Santana-RP-14-07, April 2017

Copper block Al body Steel sleeve Return/Supply pipes Vacuum pipe 30 cm

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SLIDE 18

LCLS-II BCS Functions

  • Much higher repetition rate, much higher beam power
  • These considerations require fast response, different processing and

a much wider dynamic range

  • Beam Parameter Monitoring:
  • Average Current Monitor (5 ms)
  • Average Current comparator
  • Beam Loss Monitoring:
  • Fiber Cherenkov Monitor (1 s)
  • Beam Loss Monitoring – protection of safety

devices:

  • Diamond sensor (200 µs)
  • Magnet Current Monitor

RadSynch 2017, NSRRC, Hsinchu, April 19-21, 2017

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SLIDE 19

19

BCS Devices

RadSynch 2017, NSRRC, Hsinchu, April 19-21, 2017

  • Optical Fiber
  • Cherenkov light
  • Photomultiplier (PMT) at end of fiber measures beam loss
  • Diamond Detector
  • Metallized diamond chip, 10×10×0.5 mm3
  • Fast response: output pulses of ≈5 ns
  • No accumulation from prior pulses Dynamic

range: 1–105 (B2) and 104–109 (B4)

  • Average Current Monitors

RF cavity ACMs with FPGAs to directly detect and limit beam current

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SLIDE 20

20

Status of Accelerator Radiation Protection

RadSynch 2017, NSRRC, Hsinchu, April 19-21, 2017

  • Completed:
  • Modelling of field emission from CMs
  • Dump design and associated shielding
  • Collimator design and associated shielding
  • Shielding for penetrations
  • Access Control requirements
  • Decommissioning of S0-10 of SLAC Linac
  • Radiological Environment Protection requirements
  • Air, skyshine, groundwater, residual dose rate, LCW system
  • Underway:
  • Testing and evaluation of performance of BCS (sensors,

electronics)

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SLIDE 21

21

Summary

RadSynch 2017, NSRRC, Hsinchu, April 19-21, 2017

  • Radiological analysis for LCLS-II has been conducted with extensive

use of FLUKA code and leveraging experience from LCLS-I design and operations, as well as high power beam operations

  • Sections of LCLS-II will be housed in enclosures that are designed

for lower power beam. Repurposing of the existing accelerator facility for higher average beam power has posed several challenges

  • Local shielding (penetrations) & increase of distance (fences of

beam-line modification), and Beam Containment System controls have been applied to maintain safety and provid cost-effective solutions

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SLIDE 22

22

Thank You

  • Adds a new, 4 GeV superconducting linac in an existing

SLAC tunnel, avoiding the need for excavation

  • Repetition rate up to 1 MHz (currently 120 Hz)
  • World’s only xFEL to supply uniformly-spaced train of pulses

with programmable repetition rate

  • Two new adjustable gap undulators: tunable source of X-rays
  • Intermediate X-ray energy range  studies of new materials,

chemical catalysis and biology

  • Extends the operating range to ~25 keV
  • Latest seeding technologies  fully coherent X-rays
  • Maintains the existing copper-based warm linac

RadSynch 2017, NSRRC, Hsinchu, April 19-21, 2017

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SLIDE 23

23

Test of BCS Devices

RadSynch 2017, NSRRC, Hsinchu, April 19-21, 2017

Fisher – LCLS-2 Beam-Loss Monitoring

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SLIDE 24

LCLS-II (SCRF) Baseline Parameters

Parameter nominal range units

Electron Energy 4.0 2.0 - 4.14 GeV Bunch Charge 100 10 - 300 pC Bunch Repetition Rate in Linac 0.62 0 - 0.93 MHz

  • Avg. e− beam power at linac end

0.25 0 - 1.2 MW RF frequency 1.3

  • GHz
  • Avg. CW RF gradient (powered cavities)

16

  • MV/m

Photon energy range of SXR (SCRF)

  • 0.2 - 1.3

keV Photon energy range of HXR (SCRF)

  • 1 - 5

keV Photon energy range of HXR (Cu-RF)

  • 1 - 25

keV

24

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SLIDE 25

25

Design Limits, Criteria

RadSynch 2017, NSRRC, Hsinchu, April 19-21, 2017

  • Protect workers, users, general public, and the environment on-site and off-

site from radiation of accelerator and beam operations

  • Bulk shielding

5 µSv/hr

  • Experimental hutch

0.5 µSv/hr

  • Site boundary dose

50 µSv/yr

  • Ground water activity

740 Bq/L for 3H

  • Air activation dose

1 µSv/yr

  • Maintain doses as low as reasonably achievable (ALARA)

Prompt dose rates, Residual dose rates, Impact on the environment

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SLIDE 26

26

LCLS-II Schedule

RadSynch 2017, NSRRC, Hsinchu, April 19-21, 2017

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SLIDE 27

Mis-steering: ray-trace & protection collimators

27 000277-T3_S3_17

  • Tunnels and shielding implemented in FLUKA
  • Cu-Line, HXR, SXR and DML imported from MadX twiss files into

FLUKA with MadFLUKA. This includes geometry & optics

  • Optics perturbations with one independent failure in magnetic routine:
  • Failure of a dipole:

 Field randomized between [–f, f ]: f = k*Pmax/Pmin, (includes polarity reversal)

  • Failures of a quadrupole:

 Field modulated by [-f, f], as dipole. Can reverse focusing / defocusing  Short-circuit in a pole pair  skew dipole (\ or /) with |B| =70%*g*R, (g = gradient)  Mis-alignments (up to 0.5 mm in LTU): for all quads as pre-existing condition

  • Failures of magnets on a string:

 All magnets affected by same wrong power setting  [-f, f] factor  One magnet is short-circuited  field on that magnet affected by 0≤f<1

  • Mis-steering of sextupoles, etc. assumed weak (self-shielding)

27

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SLIDE 28

Summary: LCLS-II project description

  • A new, independent electron injector
  • A new SC RF accelerator
  • Use of existing PEP-II by-pass lines
  • Redesign of muon shield
  • New Beam Transport Hall
  • Two new undulator sources
  • Hard X-ray (2-13 KeV)
  • Soft X-ray (250-2,000 eV)
  • Two (possibly three) new dumps
  • New and modified instruments for experimental stations
  • New Access Control Systems, Beam Containment system, Area

Monitors

28

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SLIDE 29

29

INTRODUCTION: LCLS-II beam-lines

CM01

CM02,03

CM04 CM15 CM16 CM33

BC1 E=250 MeV R56=-55 mm σδ=1.6 % BC2 E=1600 MeV R56=-37 mm σδ=0.38 % GUN 750 keV LH E=100 MeV R56=-14.5 mm σδ=0.05 % L0 ϕ =varies V0=100 MV Ipk=12 A σz=1.02 mm L1 ϕ = −12.7° V0=211 MV Ipk = 12 A σz=1.02 mm HL ϕ = −150° V0=64.7 MV L2 ϕ = −21° V0=1446 MV Ipk=80 A σz=0.15 mm L3 ϕ =0 V0=2206 MV Ipk=1.0 kA σz=9.0 µm BYP/LTU E=4.0 GeV R56≈0.2 mm σδ≈0.014% > 2.5-km 100-pC machine layout: April 24, 2014; v21 ASTRA run

3.9 GHz

Lf ϕ =±34 V0=202 MV Ipk=1.0 kA σz=9.0 µm

CM34,35

BC3 E=4.0 GeV R56=0 σδ=0.13 %

Crete-15 / Radiation SCRF at LCLS-II / Mario Santana Leitner - SLAC

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SLIDE 30

30 61st Annual HPS Meeting, July 17-21, 2016, Spokane, WA

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SLIDE 31

31

Beam Containment System (BCS)

RadSynch 2017, NSRRC, Hsinchu, April 19-21, 2017

  • Beam Containment System is a combination of mechanical devices and

electronic protection devices that ensure beam is confined within an approved beam channel at approved beam envelope (e.g. energy, current)

1. To monitor and limit the beam power in a beam line to the allowed value 2. To limit the losses along a beam line that is operating at its allowed power 3. To protect safety-related beam line components from damage 4. To shut off the beam if excessive radiation levels can be produced in

  • ccupied areas
  • Normal beam losses need to be addressed by shielding
  • Abnormal beam losses or operations need to be controlled by

shielding, supplemented by BCS

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SLIDE 32

FEE Dump Enclosure

Average e- Beam Current Comparator Permanent Magnets

BTM PCPM2 Main Dump

IC IC IC

Vertical Bend BYDs Horizontal Bend

Horizontal Offset Mirrors

IC

Safety Dump with BTM and ICs

PCPM0

IC IC

Shadow Wall PCPM1 BTMQUE QUE1 & 2

Magnet current monitor to match bending power of BYDs and dogleg magnets in LINAC

IC

PCPM3

32

Beam Containment for LCLS-II Electron Beams

RadSynch 2017, NSRRC, Hsinchu, April 19-21, 2017

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SLIDE 33

Radiation Streaming Through Penetrations

33

2 MW loss @ 4 GeV

South North

RadSynch 2017, NSRRC, Hsinchu, April 19-21, 2017

Waveguide penetrations: 1 m diameter (30 cm concrete + 22 cm iron)

Courtesy of Jan Blaha