O AK R IDGE N ATIONAL L ABORATORY U. S. D EPARTMENT OF E NERGY 1 Commissioning and Initial Operating...

OAK RIDGE NATIONAL LABORATORYU. S. DEPARTMENT OF ENERGY

1

Commissioning and Initial Operating Experience with the SNS Accelerator

Complex


2

Beam and Neutronics Project Completion goals were met 1013 protons

delivered to the target

The SNS Construction Project was formally Completed in June 2006

We have officially started SNS Operations

First Beam on Target, First Neutrons and Technical Project Completion Goals Met April 28, 2006


3

SNS Accelerator Complex

945 ns

1 ms macropulse

Cur

rent

mini-pulse

Cur

rent

1ms

Front-End:Produce a 1-msec

long, chopped, H- beam

1 GeV LINAC

Accumulator Ring: Compress 1 msec

long pulse to 700 nsec

Chopper system makes gaps

Ion Source2.5 MeV 1000 MeV87 MeV

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

186 MeV 387 MeV

DTLDTLRFQRFQ

Accumulator Ring

RTBT

Target

HEBT

Injection Extraction

RF

Collimators

Liquid Hg Target


4

SNS High-Level Design Parameters

Kinetic Energy GeV 1.0 Beam power on Target MW 1.4 Linac beam macro pulse duty factor % 6 Average macropulse H- current mA 26 Peak Linac Current mA 38 Linac average beam current mA 1.6 SRF cryo-module number 11+12 SRF cavity number 33+48 Peak surface field medium-beta MV/m 27.5 Peak surface field high-beta MV/m 35 Ring accumulation turns 1060 Ring current at end of accumulation A 25 Ring bunch intensity 10^14 1.5 Ring space-charge tune spread Q 0.15 Pulse length on target nsec 695

Ring is designed for 2 MW at 1 GeV; installed for 1.3 GeV (mostly)


5

The SNS Partnership

ORNL Accelerator Systems Division responsible for integration, installation, commissioning and operation


6

Spring 1999


7

Now


8

Front-End Systems

Front-End H- Injector was designed and built by LBNL

402.5 MHz Radiofrequency quadrupole accelerates beam to 2.5 MeV

Medium Energy Beam Transport matches beam to DTL1 input parameters

Front-end delivers 38 mA peak current, chopped 1 msec beam pulse

H- Ion Source has been tested at baseline SNS parameters in several endurance runs >40 mA, 1.2 msec, 60 Hz


9

Accumulator Ring and Transport Lines

Circum 248 mEnergy 1 GeVfrev 1 MHzQx, Qy 6.23,

6.20x, y -7.9, -6.9Accum turns 1060Final Intensity 1.5x1014

Peak Current 52 ARF Volts (h=1) 40 kV (h=2) 20 kVInjected p/p 0.27%Extracted p/p 0.67%

HEBT

Accumulator Ring

RTBT

Injection

Collimation

RF

Extraction

Target

Designed and built by Brookhaven National Lab


10

Ring and Transport Lines

HEBT Arc

Injection

Ring Arc

RTBT/Target


11

Target Region Within Core Vessel

Core Vessel water cooled shielding

Core Vessel Multi-channel flange

Outer Reflector Plug

Target

Target Module with jumpers

Moderators

Proton Beam


12

Normal Conducting Linac: Front-End Output Emittance and Bunch Length

MEBT inline emittance system allows routine measurement

Expect 0.3 mm mrad, rms, norm

Results ( mm mrad, rms, norm) X = 0.29 Y = 0.26

Bunch length measured with mode-locked laser system

RM

S B

unch

Len

gth

(deg

)

Rebuncher phase (deg)


13

DTL and CCL RF Setpoints by Phase Scan Signature Matching

CCL Module 2 RF Phase

BP

M P

hase

Diff

(de

g)

J. Galambos, A. Shishlo

To tune up the linac requires finding phase and amplitude setpoints for 95 RF systems within 1%/1 deg (specification)

Model-based methods utilizing time-of-flight data have been developed

Normal conducting linac phase and amplitude setpoints determined by Phase-Scan Signature Matching

Plot shows data (lines) compared to model (pts) for two CCL2 amplitudes


14

CCL Module 1 Longitudinal Bunch Shape Monitor Measurements

Measured values are close to the predicted bunch length

Measurements were motivated by earlier observations of a longer bunch, presumably due to longitudinal mismatch

BSM107 BSM111


15

Superconducting Linac Tuneup by Phase Scan

Fit varies input energy, cavity voltage and phase offset in the simulation to match measured BPM phase differences

Relies on absolute BPM phase calibration With a short, low intensity beam, results are insensitive to detuning cavities

intermediate to measurement BPMs

SCL phase scan for first cavitySolid = measured BPM phase diffDot = simulated BPM phase diffRed = cosine fit

Cavity phase

BP

M p

hase

diff


16

Low-level RF Feedforward Beam turn-on transient gives RF phase and amplitude variation

during the pulse, beyond bandwidth of feedback

LLRF Feedforward algorithms have been commissioned (Champion, Kasemir, Ma, Crofford)

Without Feed-forward With Feed-forward


17

SCL Operations: Fault Recovery (Galambos)

We have successfully tested a cavity fault recovery algorithm in which the phase of all downsteam cavities are adjusted in response to a change in setpoint of a given cavity

0

200

400

600

800

1000

1200

1400

1 5 9 13 17 21 25 29 33 37 41 45 49 53 57 61 65 69 73 77 81

Cavity

Ph

as

e C

ha

ng

e(d

eg

)

-300

-200

-100

0

100

200

300

400

1 7 13 19 25 31 37 43 49 55 61 67 73 79

Cavity

Ph

as

e C

ha

ng

e (

de

g)

-6

-4

-2

0

2

4

6

Me

as

ure

d E

rro

r (d

eg

)

Phase Change

Measured Error

Cavity 3a turned off

Final cavity phase found within 1 degree, output energy within 1 MeV

Turned on cavity 4a, reduced fields in 11 downstream cavities


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Ring/RTBT/Target Commissioning Timeline January-May 2006

Jan. 12: Received approval for beam to Extraction Dump.

Jan. 13: First beam to Injection Dump.

Jan. 14: First beam around ring.

Jan. 15: >1000 turns circulating in ring

Jan. 16: First beam to Extraction Dump.

Jan. 26: Reached 1.26E13 ppp to Extraction Dump.

Feb. 11: ~8 uC bunched beam (5x1013 ppp)

Feb. 12: ~16 uC coasting beam (1x1014 ppp)

Feb. 13: End of Ring commissioning run

April 3-7: Readiness Review for RTBT/Target

April 27: Received approval for Beam on Target

April 28: First beam on target and CD4 beam demonstration


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Accumulation and Extraction of 1.3x1013 protons/pulse (January 26, 2006)

Ring Beam Current Monitor

200 turn accumulation

extraction

Extraction Dump Current Monitor


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Ring Orbit Correction: H,V Bumps are Due to Injection Kickers

Horizontal Orbit

BPM Amplitude

Vertical Orbit


21

Ring Optics Measurements: Betatron Phase Advance and Chromaticity

Vert Horiz

Natural Chromaticity (Design)

-6.9 -7.9

Natural Chromaticity (Measured)

-7.2 -8.2

Corrected Chromaticity (Meas)

0.0 0.1

Horizontal Fit

-30

-20

-10

0

10

20

30

1 4 7 10 13 16 19 22 25 28 31 34 37 40 43

Beam Position Monitor

Bet

atro

n P

has

e E

rro

r (d

egre

es)

Horizontal Data

Horizontal Fit

Vertical Fit

-30

-20

-10

0

10

20

30

1 4 7 10 13 16 19 22 25 28 31 34 37 40 43

Beam Position Monitor

Be

tatr

on

Ph

as

e E

rro

r (d

eg

ree

s)

Vertical Data

Vertical Fit

Plots show measured betatron phase error vs. model-based fit

Data indicates that the linear lattice is already very close to design


22

High Intensity Studies (Danilov, Cousineau, Plum)

Beam intensity records (protons/pulse): 5x1013 in bunched beam, transported to

target 1x1014 unbunched, coasting beam

We searched for instabilities by i) delaying extraction, ii) operating with zero chromaticity, iii) storing a coasting beam

No instabilities seen thus far in “normal” conditions

See instability centered at 6 MHz, growth rate 860 us for 1014 protons in the ring, driven, as predicted by extraction kicker impedance Zcalc 22-30 kOhm/m Zmeas 28 kOhm/m.

In coasting beam also see very fast instability at 0.2-1x1014 protons in the ring, consistent with e-p. Growth rate 20-200 turns. f 30-80 MHz depending on beam conditions.

Scaling these observations to nominal operating conditions predicts threshold > 2 MW for extraction kicker (as previously predicted)

0 50 100 1502

2.5

3

3.5

4

4.5

5

5.5

6

Turns

Log

(ma

gin

itu

de(7

5th

Ha

rmo

nic

))

Evolution of 75th Harmonic

Slow: Extraction Kicker

Fast: electron-proton


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Phase Space PaintingStripping Foil

Injected BeamInitial Closed

OrbitFinal Closed

Orbit

X

px

Wei et. al., PAC 2001, 2560

X-Y space after 1060 Turns


24

Phase Space Painting

65 mm 80 mm

Beam on Target View Screen

Beam profiles in RTBT


25

Summary of Achieved Beam Parameters Parameter Baseline/

DesignAchieved in Commissioning/AP

Achieved in Operation

Units

Linac Transverse Output Emittance

0.4 0.3 (H), 0.3 (V) 0.4 mm-mrad (rms,norm)

CCL1 bunch length 3 4 4 degrees rms

Linac Peak Current 38 > 38 20 mA

Linac Output Energy 1000 1012 890 MeV

Linac Average Current 1.6 1.05 (DTL1 run) 0.003 (SCL run)

0.067 mA

Linac H-/pulse 1.6x1014 1.3x1014 (DTL1) 8.0x1013 (SCL run)1.0x1014 (Ring run)

4.3x1013 Ions/pulse

Linac Pulse length/Rep-rate/Duty Factor

1.0/60/6.0 1.0/60/3.8 (DTL1 run) 0.85/0.2/0.017 (SCL)

0.6/5/0.3 msec/Hz/%

Extracted protons/pulse 1.5x1014 0.96x1014 0.43x1014 Protons/pulse

Beam Power 1440 4 60 kW


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Beam-Power-on-Target HistoryB

eam

Po

we

r [0

-65

kW

]

Beam power administratively limited to 10 kW until November 8

Feb 1, 2007May 1, 2006


27

FY 2007 Integrated Beam Power by Day and Cumulative

6.3 MW-hrs delivered in Run 2007-1


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Technical Challenges: Equipment Reliability Beam Chopper Systems

Repeated failures in Low-energy and Medium-energy Beam Transport chopper systems

New, more robust, designs will be designed and manufactured this year (FY07 Accelerator Improvement Project)

High-Voltage Converter Modulators A number of weak components limit MTBF to 2700 Hrs Several prototype improvements are in test in single operational units Improvements will be deployed this year on full system of 14 modulators (FY07

Accelerator Improvement Project) Ion Source and Low Energy Beam Transport System Water Systems

Problems associated with clogging flow restrictors, failed gaskets, poor conductivity monitoring and control, etc.

Reliability improvements have been underway since CD-4 (also FY07 AIP) Cryogenic Moderator System

Thermal capacity degraded in 3 week cycle prior to December 2006 Manufacturer attempted repair in December Capacity improved, but some sign of degradation remains

Mercury Pump Seal failed end of November Operating the pump now with failed seal, mitigated by installation of a cover plate to

direct gas to the Mercury Off-Gas Treatment System Replacement Mercury Pump in expected to be available for installation in September


29

Technical Challenges: Beam Power Beam losses must be kept below 1 Watt/m to limit residual activation

We measure higher than desired losses in the Ring Injection area We are unable to simultaneously transport waste beams (from stripping

process) to the injection dump and properly accumulate in the ring Internal Review of Injection Dump performance was held in November and

follow-up meeting in December Short-term fixes allow >100 kW operation; mid-term fixes (April 2007) are in

preparation; long-term fix requires redesign of injection dump beamline and 2 new magnets

An aggressive accelerator physics program has reduced losses and activation while allowing increased beam power

We are not operating 9 Superconducting RF cavities (out of 81) out of concern for potential failures

Recent tests indicate that 6 of these 9 cavities are operable up to 15 Hz repetition rate

Those tests also show that the behaviour of individual cavities is the same at higher repetition rates, up to the full 60 Hz

We are building infrastructure to provide cryomodule repair and maintenance capabilities on-site. We are formulating plans to restore operation of all cavities, and to procure spare cryomodules


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Outlook: Performance Goals

0

500

1000

1500

2000

2500

0 12 24 36Months

Bea

m P

ower

(kW

), P

rodu

ctio

n H

rs

50

55

60

65

70

75

80

85

90

95

Rel

iabi

lity

Beam Power GoalNeutron Production HoursReliability

FY08FY07 FY09

SNS Beam Power Upgrade Project will increase linac output energy to 1.3 GeV and provide 3 MW beam power


31

E-P Feedback Experiment at the PSR We formed a collaboration to carry out an experimental test of

active damping of the e-p instability at the LANL PSR (ORNL, LBNL, IU, LANL)

We deployed a broadband transverse feedback system designed and built by ORNL/SNS and demonstrated for the first time damping of an e-p instability in a long-bunch machine

We observed a 30% increase in e-p instability threshold with feedback on.


32

We have observed > 90% H- to proton stripping efficiency in proof-of-principle tests at SNS

Laser Beam

H- proton

H0 H0*

Step 1: Lorentz Stripping

Step 2: Laser Excitation Step 3: Lorentz Stripping

High-field Dipole Magnet

High-field Dipole Magnet

H- H0 + e- H0 (n=1) + H0* (n=3) H0* p + e-

Laser-Stripping Injection Proof-of-Principle Experiment

H- to protons


33

Yes, We’ve Had a Few Surprises RFQ resonant frequency shifted by 100 kHz

Never found the cause; retuned in 2003

Bunch length 3x design in CCL1; also had difficulty keeping DTL5 at design field Found a charred piece of paper in DTL Tank 5 in 2004

Large local losses and poor trajectory near SCL/HEBT transition Found large dipole deflection with orbit response studies Found current shunted around one quad coil

Beam is rotated about 6 degrees on target view screen

Excessive fundamental power through two SCL HOM feedthroughs; others impacted

Large local losses in injection dump line


34

Summary Completed 7 beam commissioning runs, amounting to

more than 1 year of dedicated beam commissioning and operating time

Achieved beam and neutron project completion requirements within project schedule

SNS construction project was formally completed in June 2006 on-budget and on-schedule

We are now in the early operations stage with local users

We are beginning to ramp up the beam power of the SNS accelerator complex


35

SNS Beam Diagnostic SystemsRING

44 Position 2 Ionization Profile70 Loss 1 Current 5 Electron Det. 12 FBLM2 Wire 1 Beam in Gap2 Video 1 Tune

RING44 Position 2 Ionization Profile70 Loss 1 Current 5 Electron Det. 12 FBLM2 Wire 1 Beam in Gap2 Video 1 Tune

SCL32 Position 86 Loss 9 Laser Wire24 PMT Neutron

SCL32 Position 86 Loss 9 Laser Wire24 PMT Neutron

RTBT17 Position36 Loss4 Current5 Wire1 Harp3 FBLM

RTBT17 Position36 Loss4 Current5 Wire1 Harp3 FBLM

HEBT29 Position 1 Prototype Wire-S46 BLM, 3 FBLM 4 Current

HEBT29 Position 1 Prototype Wire-S46 BLM, 3 FBLM 4 Current

IDump1 Position1 Wire 1 Current6 BLM

IDump1 Position1 Wire 1 Current6 BLM

EDump1 Current 4 Loss 1 Wire

EDump1 Current 4 Loss 1 Wire

LDump6 Loss6 Position1 Wire ,1 BCM

LDump6 Loss6 Position1 Wire ,1 BCM

CCL/SCL Transition2 Position 1 Wire1 Loss 1 Current

CCL/SCL Transition2 Position 1 Wire1 Loss 1 Current

CCL10 Position 9 Wire 8 Neutron, 3BSM,

2 Thermal28 Loss 3 Bunch

1 Faraday Cup 1 Current

CCL10 Position 9 Wire 8 Neutron, 3BSM,

2 Thermal28 Loss 3 Bunch

1 Faraday Cup 1 Current

OperationalOperational MEBT6 Position2 Current5 Wires2 Thermal Neutron3 PMT Neutron 1 fast faraday cup1 faraday/beam stopD-box videoD-box emittance D-box beam stop D-box apertureDifferential BCM

MEBT6 Position2 Current5 Wires2 Thermal Neutron3 PMT Neutron 1 fast faraday cup1 faraday/beam stopD-box videoD-box emittance D-box beam stop D-box apertureDifferential BCM

DTL10 Position 5 Wire 12 Loss 5 Faraday Cup 6 Current6 Thermal and 12 PMT Neutron

DTL10 Position 5 Wire 12 Loss 5 Faraday Cup 6 Current6 Thermal and 12 PMT Neutron

Not OperatingNot Operating


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Baseline SNS Ion Source Performance • LBNL H- ion source + ORNL antennas• Source performed well during SNS

commissioning.• Successful commissioning would not

be possible without use of longer-lived antennas.

• 10-40 mA routinely delivered at ~0.1% duty-factor.

• Availability improved: 86% ~100% during later commissioning periods (target comm: 77 days).

• Largest availability gain redesigning LEBT insulatorsAntennas: Welton et al,

RSI 73 (2002) 1008

+

0

5

10

15

20

25

30

35

40

20-Sep 25-Sep 30-Sep 5-Oct 10-Oct 15-Oct0

5

10

15

20

25

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35

40

45

27-Jun 2-Jul 7-Jul 12-Jul 17-Jul 22-Jul

Ave

rage

Bea

m C

urre

nt (m

A)

Beam attenuation ~5 mA/day Run #9 ran for 16 days / 33 mA / 0.4 mA/day.

3 Typical Test Runs Our Best Run(employs new operating procedure)

Catastrophic antenna failure

• ~10 lifetime tests performed at full 7% duty-factor and max current.

• Best results shown• Outcome: Insufficient beam

current, frequent antenna failures and poor beam stability with time

• Vigorous R&D program to meet SNS operational requirement of 40 mA and SNS-PUP requirement of 60 mA.


37

Recent Ion Source R&D Accomplishments Ionization Cone

Cs injection collar

Air ductCs

Line

Extractor electrode

ions

0.0

10.0

20.0

30.0

40.0

50.0

60.0

0 20 40 60 80

RF Power (kW)

H-

Cu

rren

t (m

A)

uncesiated

cesiated

Elemental Cs system 65 mA-1.2 ms, 70 mA-0.2 ms pulses

achieved at 10Hz!

~2x increase in RF power efficiency.

Multi-day runs show excellent beam stability.

Multiple cesiations show excellent reproducibility.

~5% droop and good ~30 us rise times.

Beam emittance is expected to be similar to baseline source.

Al2O3 insulator

Anode

Cooling channel

Plasma stream

Cathode Ions

0

10

20

30

40

50

60

70

80

0 20 40 60 80 100

RF Power (kW)

H-

Cu

rren

t (m

A)

Peak

Average

Multi-year lifetime achieved at DESY at <1% duty-factor

Plasma gun enhances H- ~50%

51 mA – 0.2 ms pulses achieved with no Cs and no B-field confinement.

65 mA – 0.2 ms, 50 mA – 1.2 ms pulses achieved with Cs and no confinement.

Welton et al, LINAC 2006, Knoxville

External Antenna & Plasma Gun

Welton et al, LINAC 2006, Knoxville


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Energy Stability – Pulse to Pulse (J. Galambos)

RMS energy difference jitter is 0.35 MeV, extreme = + 1.3 MeV

Parameter list requirement is max jitter < +1.5 MeV

865 MeV beam

~ 1000 pulses

20 sec pulse

12 mA beam


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SCL Laser Profile Measurements

SCL laser profiles (H + V) were available at 7 locations 3 at medium beta entrance, 3 at high beta entrance and 1

at the high beta end

Measured horizontal profile after SCL cryomodule 4


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Neutrons: 4-methyl pyridine N-oxide 5 kWatt, 3 hour, ¼ detector, T = 3 K

4 eV


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The Spallation Neutron Source The SNS is a short-pulse neutron source, driven by a 1.4 MW proton accelerator 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

Stepping stone to other high power facilities

O AK R IDGE N ATIONAL L ABORATORY U. S. D EPARTMENT OF E NERGY 1 Commissioning and Initial Operating...

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Transcript of O AK R IDGE N ATIONAL L ABORATORY U. S. D EPARTMENT OF E NERGY 1 Commissioning and Initial Operating...