Overview of Beam Instrumentations for High-Power Operation of the Spallation Neutron Source

Managed by UT-Battellefor the Department of Energy

Overview of Beam Instrumentations for High-Power Operation of the Spallation

Neutron Source

Saeed Assadi for SNS B.I. Group

Beam Instrumentation Group Leaser

SNS/ORNL

2 Managed by UT-Battellefor the Department of Energy WGF01- HB2008 8/26/2008

OUTLINE

Overview of Beam Instruments

SCL Laser Profile Monitor Project

Recent results

Challenge

Future plan


The Spallation Neutron Source


Liquid Hg Target

SNS Accelerator Complex

Front-End:Produce a 1-msec

long, chopped, H- beam

1 GeV LINAC

Accumulator Ring: Compress 1 msec long

pulse to 700 nsec

Ion Source2.5 MeV 1000 MeV87 MeV

CCLCCL SRF, =0.61SRF, =0.61 SRF, =0.81SRF, =0.81

186 MeV 387 MeV

DTLDTLRFQRFQ

RTBT

HEBT

InjectionExtraction

RF

945 ns

1 ms macro-pulse

Cur

rent

mini-pulse

Chopper system makes gaps

Accumulation 700 nsecPulse


Interceptive Beam Instrumentation Systems

RING 2 Wire-deleted

RING 2 Wire-deleted

SCLSCL

RTBT5 WireScanners

1 Harp1 RTBT VideoTarget Video

RTBT5 WireScanners

1 Harp1 RTBT VideoTarget Video

HEBT5 Wire Scanners

2 BSM

HEBT5 Wire Scanners

2 BSM

IDump2 Wire 2 IDump Video

IDump2 Wire 2 IDump Video

Edump 1 WireEdump 1 Wire

LDump1 Wire LDump1 Wire

CCL/SCL Transition 1 Wire

CCL/SCL Transition 1 Wire

CCL 8 Wire , 4BSM,1 Faraday Cup

CCL 8 Wire , 4BSM,1 Faraday Cup

OperationalOperational

MEBT5 WiresD-box emittance D-box beam stop D-box aperture1 fast faraday cup1 faraday/beam stopD-box video

MEBT5 WiresD-box emittance D-box beam stop D-box aperture1 fast faraday cup1 faraday/beam stopD-box video

DTL5 Wire5 Faraday Cup

DTL5 Wire5 Faraday Cup


Non-Interceptive Beam Instrumentation Systems

RING2 Electron Profile Scanner 5 Electron Det. 12 FBLM1 Beam in Gap Monitor1 Tune, 84 BLMs, 4 NDs2 Transverse feedback system

RING2 Electron Profile Scanner 5 Electron Det. 12 FBLM1 Beam in Gap Monitor1 Tune, 84 BLMs, 4 NDs2 Transverse feedback system

SCL32 Position 86 Loss 9 Laser Wire1 Laser Wire24 PMT Neutron

SCL32 Position 86 Loss 9 Laser Wire1 Laser Wire24 PMT Neutron

RTBT1 Movable Harp3 FBLM26 BPMs26 BLMs

RTBT1 Movable Harp3 FBLM26 BPMs26 BLMs

HEBT29 Position 1 Laser Beam in-gap1 Laser emittance sys48 BLMs, 4FBLM

HEBT29 Position 1 Laser Beam in-gap1 Laser emittance sys48 BLMs, 4FBLM

IDump1 Position1 Current2 BLM

IDump1 Position1 Current2 BLM

EDump 4 BLM, 1 BCM

EDump 4 BLM, 1 BCM

LDump2 Loss1 Wire ,1 BCM5 position

LDump2 Loss1 Wire ,1 BCM5 position

CCL/SCL Transition

2 Position1 Loss 1 Current

CCL/SCL Transition

2 Position1 Loss 1 Current

CCL8 Neutron, 2 Thermal48 Loss

CCL8 Neutron, 2 Thermal48 Loss

OperationalOperationalMEBT

2 Thermal Neutron3 PMT Neutron D-box Mode-lock laser2 Beam-Gap Monitor [ChuMPS]6 BPMs2 BCMs1 Mode-lock laser

MEBT2 Thermal Neutron3 PMT Neutron D-box Mode-lock laser2 Beam-Gap Monitor [ChuMPS]6 BPMs2 BCMs1 Mode-lock laser

DTL2 Beam-Gap Monitor [ChuMPS]3 Diff BCM Monitor6 Thermal and 12 PMT Neutron6 Current, 12 BLMs

DTL2 Beam-Gap Monitor [ChuMPS]3 Diff BCM Monitor6 Thermal and 12 PMT Neutron6 Current, 12 BLMs

Not OperatingNot Operating


Quick History and Facts about SNS

The SNS is a short-pulse neutron source, driven by a 1.4 MW proton accelerator [ presently at .54 MW].

SNS will be the world’s leading facility for neutron scattering research with peak neutron flux ~20–100x ILL, Grenoble

SNS construction project, a collaboration of six US DOE labs, was funded through DOE-BES at a cost of 1.4 B$

SNS will have 8x beam power of ISIS, the world’s leading pulsed source user facility,Stepping stone to other high power facilities, expected to achieve 1.4 MW in two years.


Motivation to Add &/or Modify More Beam Instruments

Improve reliability

Improve user friendliness – i.e. automation, additional features –

Support, diagnose “unexpected” events – i.e. Spark detectors, LEBT and RFQ RGAs

Accelerator Physics requests – Laser emittance system.

Allow “parasitic” studies; IPM, electron profile monitor. Different types of BLMs.


Continue: Motivation to Add &/or Modify More Beam Instruments

60 Hz Beam Accounting [Never was in the plan]

Low Energy Beam Loss Measurements , WGF4- A. Zhukov’s talk

Differential Current Measurements in DTL/CCL

High Power Operations.– e/p Instabilities, use of digital active transverse feedback system for the Ring. WG F- (wed) – Craig Deibele’s talk

Ring Electron Profile Monitor, BINP collaboration with SNS, initial results by W. Blokland in this talk.

Computation of Space-Charge Effects in Allison Scanner and Its Application to the Measurement of Emittance by Timofey Gorlov


Laser Striping Experiment

SCL Laser ProfileMonitors, 9-stations

MEBT 3-D LaserProfile Monitor

1) MEBT Mode-lock laser initially in 1-D – 9/20042) SCL Nd:YAG 1064 nm Laser, 9-station – 9/20053) Laser Stripping test Nd:YAG, 3ed harmonic -- 8/20054) Working on making SCL Laser system turn-key -- to present

ORNL-SNS Laser Diagnostic Activities

4M 4H 1D

Laser Emittance


What does the Laser do? Photo-neutralization

Requirements• High peak power• Small spot size• Transverse scan• Temporal stability• Detection

h H- H0 + e

Cross-section is well known therefore stripping efficiency calculation is a matter of algebraic manipulation

-H-

time

12nsIbeam


Principle of Laser Wire, direct electron current measurement at SNS.

hH-

N

S

Faraday Cup

H0

e

H0

Photodetachment

• Detected electron number is proportional to the ion density


Redundant Lasers are available for the SCL.

Q-switched Nd:YAG laser = 1.06 m frep = 30 Hz, Tw = 7 ns

Ep = 50 – 200 mJInjection seededTiming synchronized to SCL

Laser Room

• High pulse energy

• Small spot size

• Single wavelength

• Pointing stability

• Temporal stability

Requirements:


SCL

1 2 3 4 5 321712 13 14 15

250 m 227 m 25 m160 m

LR Laser room

Laser wire station

Cryomodule number

Camera

Mirror

Power meter32

LR

Ring

Layout of the SCL Laser Wire System

CCLDTL

Target

MEBT

• 4 LW from 200 MeV

• 4 LW from 450 MeV

• 1 LW at 1 GeV


Q-switched Nd:YAG laser1064 nm30 Hz7 nsUp to 1.5 JInjection seeded

SCL Laser Transport Line


Schematic of Laser Wire Station Optics

Mirror

Lens

Photodiode

Beam Dump

Flip-Mirror

From LTL

V-scan

H-scan

Ion Beam


Top-Level Software Controls all Stations and collects Data.

Profile Measurement LW Station Diagnostics

User specifies station, axis, scanning range/step/ave. number, controls timing, and data acquisition

User monitors laser beam position, lens focus, electron collector output raw signal


0 1 2 3 4 5 6 7 8 9 10 11 12 13 14

Magnet Current (A)

LW Station 02

LW Station 15

LW Station 32

Falling edge cut

Rising edge cut

Normal profile

Effects of LW Magnet Current

0

2

4

6

8

10

12

14

0 2 4 6 8 10

Laser Wire Station #

Mag

net

Cur

rent

(A

)


Vertical Beam Profile Measurement at LW32

12.912.411.911.410.910.49.99.48.98.47.97.4

Magnet Current

(A)

14 16 18 20 22 24 26 28 30

Vertical Position (mm)

Det

ecto

r O

utpu

t (10

0 m

V/d

iv)

One challenge that is solved Effects of LW Magnet Current


Mini-pulse #1 #100 #200 #300

Advantage of Laser is to be able to scan the entire Macro-pulse.


Beam Profile Measurements

0

0.1

0.2

0.3

0.4

0.5

0.6

10 15 20 25 30

Position (mm)

Sig

nal (

V)

0

0.1

0.2

0.3

10 15 20 25 30 35

Position (mm)

Sig

nal (

V)

0

0.1

0.2

0.3

0.4

10 15 20 25 30

Position (mm)

Sig

nal (

V)

0

0.1

0.2

0.3

0.4

0.5

10 15 20 25 30

Position (mm)S

igna

l (V

)

0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

15 20 25 30 35

Position (mm)

Sig

nal (

V)

0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

10 15 20 25 30

Position (mm)

Sig

nal (

V)

LW1

LW5

LW9


Ion beamLaser beam

f

S

Ion beam

YdLaser beam

f

S

Laser beam shifts on the lens Laser beam shifts on the lens surfacesurface

Laser beam shifts + Ion beam Laser beam shifts + Ion beam shifts from waistshifts from waist

Realistic Laser Beam with respect to H-


Ion beam

YdLaser beam

f

S

Measured profile as a function of lens position at LW14V

0

0.1

0.2

0.3

0.4

0.5

18 20 22 24 26 28 30

Position

Am

plitu

de (

V)

Yd=0 Yd=5mm Yd=10mm

Challenge! Experimental Measurements

Why do we get poor profiles in this case


Current Laser Wire Box

14

11.5

12

11.5

12

13.5

4.5

4

2.75

2-3/8

2.5

2.5

2-3

/8

5.75

3.5

3.25

3.25 3.5 5

6.5

6.5

2.75

2.75

1

1

rear front

6.75

7.25


Revised Laser Wire Box Design to Bring Larger Travel Range

14

11.5

12

11.5

12

13.5

4.5

4

2.75

2-3/8

2.5

2.5

2-3

/8

3.25

3.25 3.5 5

6.5

6.5

2.75

2.75

1

1

6.75

7.25


SUMMARY of Laser Profile Monitor

Profiles have been measured at all 9 stations

Operational parameters have been investigated and optimized

Software platform has been improved

Issues of radiation and stability are looked into and solutions are provided

Future plan – Secure system reliability– Optimize/document operational procedure– Identify technical problems and work on solutions


600750

MCP

Phosphor screen

Photo camera

Layout of the proposed EBP for SNS Accumulator Ring by BINP

Electron Gun

DeflectorQuadrupole

lens

Proton beam

Electron beam Transverse Profile Monitor

28 Managed by UT-Battellefor the Department of Energy WGF01- HB2008 8/26/2008 28

Collaboration on Design and Construction of Electron Beam Profile MonitorBetween SNS-ORNL and BINP, Novosibirsk, Russia has started

Probe beam:

Energy=75keV,

Scan.-parallel,

3rd ,4th quads - ON

Proton beam:

Energy=1GeV

Np=1*1013

Transverse size r=1.5cm

Round uniform transverse distribution

-0,2

0

0,2

0,4

0,6

0,8

1

1,2

-3 -2 -1 0 1 2 3

Simulation

Blue line – theoretical profile,

Magenta + square – reconstructed profile

Alexander Starostenko


Horizontal Profile after 500 turn, 8 Micro-Coulomb of charge in the Ring.


Vertical Profile after 500 turn, 8 Micro-Coulomb of charge in the Ring ---- Another useful tool!


Thanks

Documents

Overview of Beam Instrumentations for High-Power Operation of the Spallation Neutron Source