Linac4 commissioning strategies (part I, up to 12MeV) G Bellodi (BE-ABP-HSL) , Jim Stovall & L4 beam dynamics group

Timeline

RFQ

MEBT

TANK1

TANK2 + TANK3

01/2011

04/2011

07/2012

01/2013?

Linac4 test stand area

Linac4 tunnel

very important to achieve beam quality : non periodical

lattice, larger beam modulations, important

space charge effects, ‘new’ technology not quite fully

established

not many handles to play with (V vs T)

all PMQs for transverse planes, find correct

matching between tanks and longitudinal RF set

points

Permanent diagnostics: MEBT

TransformersWire scanners

clamp-on steerers

Temporary diagnostics : movable test bench

Emittance meter, spectrometer, 2-3 PUs, 2-3 BCTs, Feschenko, halo monitor

for machine commissioning & to calibrate permanent diagnostics (to be used in operation)

BeamsNominal beam Commissioning full Commissioning

pencil Pulse length 400 ms 50-100ms 50-100msRep rate 2Hz 1Hz 1HzMax beam current 65mA 65mA 1 mA (? tbd)Average beam current (after chopping) 40 mA 40 mA

Tr. beam emittances at RFQ output (RMS norm) 0.25 mm mrad 0.25 mm mrad 0.05 mm mrad

Longitudinal emittances 0.13 deg MeV 0.13 deg MeV 0.18 deg MeV

..& procedures:

1) Transverse plane:

• Steering/orbit correction • Quad tuning • Transverse beam matching

2) Longitudinal plane:

• RF amplitude/phase scans • longitudinal matching

MEBT commissioning path

0 – beam transport, orbit correction, preliminary quad setting

1 – longitudinal plane characterisation, set RF f/A points for buncher cavities

2 – transverse beam matching , quad tuning, halo studies

3 – chopper functionality (time integrated)

4 – chopper functionality (time resolved)

phase 0 – transport & steering

SETUP: low current & pencil beam, chopper plates OFF

AIM: ensure beam transport through MEBT and test bench, measure beam offsets and perform orbit correction, preliminary quad setting

PROCEDURE: Observe beam profiles on wire scanners, beam position signals on BPMs and measure (differential current) transmission at the BCTs. Measure quadrupole response matrix, beam offsets and perform orbit correction.

1 2 3 40

0.2

0.4

0.6

0.8

1

1.2

10mA20mA30mA40mA50mA65mA80mA

# TRAFO

rela

tive

curr

ent

Relative readings of BCTs 1, 2 (MEBT) 3,4 (test stand) for several input currents [bunchers off- no retuning]

Response matrix at WS

-0.6 -0.4 -0.2 0 0.2 0.4 0.6

-0.015

-0.01

-0.005

0

0.005

0.01

0.015

QDA3010 field curves

80%90%100%110%120%

y beam offset at Q [cm]

y at

WS

[m]

Measure beam position at WS while scanning quadrupole field gradients and derive beam offsets inside quads . Correct the orbit with steerers.

phase 1: longitudinalAIM: characterise buncher cavities, set RF phase and amplitude points, measure beam average energy/ energy spread

PROCEDURE: On the spectrometer line (pencil beam, chopper plates OFF) : Find RF phase point: set max voltage on cavity and spectrometer Bfield for 3 MeV (NMR probe). Measure beam displacement on SEM while scanning over phase: beam centered for f=±90o Find RF amplitude point: set phase to 0deg and measure beam displacement on SEM while scanning over voltage values.

STEPS: i) Calibrate buncher1 – bunchers 2, 3 off ii) Calibrate buncher2 – buncher1 at nominal, buncher3 off iii) Calibrate buncher3 – bunchers 1, 2 at nominal

f=±90deg no energy gain

f=0, 180deg max energy deviation

-110 -105 -100 -95 -90 -85 -80 -75 -70

-10

-5

0

5

10

-30-20-100102030

f(x) = 2.64167901234569 x + 237.687255555557

f(x) = 0.541359382716049 x + 48.0841844444445

buncher1 phase

phase [deg]

dx [m

m]

dE [k

eV]

30 40 50 60 70 80 90 100 110 120 130

-10

-5

0

5

10

f(x) = 0.1923703 x − 16.0894821666667

buncher1 voltage

cavity voltage [kV]

dx [m

m]

-110 -105 -100 -95 -90 -85 -80 -75 -70

-10

-5

0

5

10

f(x) = 0.567542654320988 x + 50.1604733333333

buncher 2 phase

phase [deg]

dx [m

m]

40 50 60 70 80 90 100 110 120 130

-10-505

1015

f(x) = 0.216712583333333 x − 15.0703918055556

buncher2 voltage

voltage [kV]

dx [m

m]

-110 -105 -100 -95 -90 -85 -80 -75 -70

-10

-5

0

5

10

f(x) = 0.739115119395712 x + 66.5503484758772

buncher3 phase

phase [deg]

dx [m

m] 40 60 80 100 120 140 160 180 200

-20-15-10

-505

10

f(x) = 0.201630555555556 x − 31.4925188888889

buncher3 voltage

voltage [kV]

dx [m

m]

Sensitivity: 0.5mm per deg offset, 0.2mm for 1kV offset/ ok for SEM grid resolution

Crosscheck with TOF measurement of average beam energy BPMs phase calibration

TOF measurement

PUs at s=4318, 5148, 6275 mm (from start of chopper line)

Case1 : df=2deg, dL=0 Case2 : df=1deg dL=0.3mm

PUs 3 MeV 12 MeV

Case1 Case2 Case1 Case2

1-2 3.50 keV 2.57 keV 23.8 keV 14.1 keV2-3 2.58 1.90 17.5 10.41-3 1.48 1.09 10.1 6

Sensitivity:

~ok for case2 and 1‰ sensitivity requirement

Beam debunching vs current

0 10 20 30 40 50 60 70 80 900

20406080

100120140160 PU1

no focusingfocusingbuncher 1 onbuncher 1+2

current [mA]

RMS

phas

e sp

read

[deg

]

0 10 20 30 40 50 60 70 80 900

50

100

150

200

PU2

no focusingfocusingbuncher 1 onbuncher 1+2

current [mA]

RMS

phas

e sp

read

[deg

]

0 10 20 30 40 50 60 70 80 900

50

100

150

200

250

PU3

no focusingfocusingbuncher 1 onbuncher 1+2

current [mA]

RMS

phas

e sp

read

[deg

]

AIM: characterise longitudinal plane, find matching point to DTL (full current beam, chopper plates OFF ) Feshenko monitor calibration (bkgnd subtraction of detached e-)

PROCEDURE:Measure bunch profiles with Feschenko monitor while varying buncher settings.3-points emittance measurement with low intensity beam?

0.600000000000001 1.1 1.610

15

20

25

30

35

40

45

50 buncher 1buncher 2buncher 3

fraction of buncher voltage

RMS

phas

e sp

read

[deg

]

-120-100 -80 -60 -40 -20 0 20 40 60 80

100120

0

500

1000

1500

2000

2500

3000

3500

MEBT buncher1 on Feshenko

90%100%110%

phase [deg]

Freq

uenc

y

s=35,30,26 deg

Longitudinal matching with Feshenko

Gaussian fitted RMS spread vs buncher settings 1 deg phase resolution

phase 2 – transverse beam matching

SETUP: full current beam, chopper plates OFF

AIM: establish transverse matching conditions, find initial Twiss parameters, quad tuning

PROCEDURE:Quadrupole gradients scan technique with measurement of beam profiles at WS, transmission on BCTs and emittances on scanner

STEPS:

i) RFQ to MEBT : 1st FODO (L4L.QDA3010, L4L.QFA3030,L4L.QDA3050,L4L.QFA3070)

ii) MEBT central quads

iii) MEBT to DTL : last FODO (L4L.QDD3170, L4L.QFD3180,L4L.QDA3200,L4L.QDA3220)

RFQ to MEBT quad gradient scan (±20%)

Nice signature for quad2, not so clear for other quads Clear peak signature, can tune to

few % level if we can resolve 1% in differential beam current with BCT

Beam measured on MEBT diagnostics: WS and BCTFairly ideal simulation case, no mismatch, no errors; only one quad gradient varied at any one time (others assumed at nominal settings)

MEBT to DTL classic quad gradient scan (±20%) Measurements on test bench installed after Tank1

Fairly ideal simulation case, no mismatch, no errors; only one quad gradient varied at any one time

Good if already close to the solution…

0.700000000000001 1.22.500E-07

3.000E-07

3.500E-07

4.000E-07

4.500E-07

5.000E-07

RMS x emittance

q8q9q10q11

gradient ratio

emitt

ance

[m ra

d]

0.700000000000001 1.22.000E-072.500E-073.000E-073.500E-074.000E-074.500E-075.000E-07

RMS y emittance

q8q9q10q11

gradient ratio

emitt

ance

[m ra

d]

0.700000000000001 1.21.00E-03

1.50E-03

2.00E-03

2.50E-03

3.00E-03

3.50E-03

RMS x size

q8q9q10q11

gradient ratio

size

[m]

0.700000000000001 1.27.50E-04

8.50E-04

9.50E-04

1.05E-03

1.15E-03

1.25E-03

RMS y size

q8q9q10q11

gradient ratio

size

[m]

No clear signature with available diagnostics resolution [ 0.1mm mrad / 0.5mm]…

MEBT to DTL random quad gradient scan (±20%)

0.750000000000001 1.250.00E+00

2.00E-07

4.00E-07

6.00E-07

8.00E-07

1.00E-06

1.20E-06

q8, rms x emitt

gradient ratio

emitt

ance

[m ra

d]

0.750000000000001 1.250.00E+002.00E-074.00E-076.00E-078.00E-071.00E-061.20E-06

q9, rms x emitt

gradient ratio

emitt

ance

[m ra

d]

0.750000000000001 1.250.00E+00

2.00E-07

4.00E-07

6.00E-07

8.00E-07

1.00E-06

1.20E-06

q10, rms x emitt

gradient ratio

emitt

ance

[m ra

d]

0.750000000000001 1.250.00E+00

2.00E-07

4.00E-07

6.00E-07

8.00E-07

1.00E-06

1.20E-06

q11, rms x emitt

gradient ratio

emitt

ance

[m ra

d]

Apart from Q10, no clean single knob for tuning, but rather flat signal

Beam measured on test bench installed after Tank1no mismatch, no errors

All quads randomly varied at the same time

Multi-variables approach (offline/online?)

0.0015 0.002 0.0025 0.003 0.0035 0.004 0.00450

0.0005

0.001

0.0015

0.002

0.0025

x size

y siz

e

0.0015 0.002 0.0025 0.003 0.0035 0.004 0.00450.00E+00

2.00E-07

4.00E-07

6.00E-07

8.00E-07

1.00E-06

1.20E-06

x size

emitt

x R

MS

Build a statistical database of cases. Cut in multivariable space to reduce data sample and plot data projectionsExample: e RMS (x,y) < 0.4 mm mrad & T> 95%

0.8 0.85 0.9 0.95 1 1.05 1.1 1.15 1.2 More0

1

2

3

4

5

6

7

8

q9

Gradient factor

Freq

uenc

y

Mean ≈1 , s≈10%

0.8 0.85 0.9 0.95 1 1.05 1.1 1.15 1.2 More0

1

2

3

4

5

6

7

8

q8

gradient factor

freq

uenc

y

Automated transverse beam matching? (a` la SNS/JPARC )

WSWS Bench/WS?

High level software application to:•Compare measured and model predicted beam sizes in the MEBT for a variety ofMEBT magnet settings•Solve for MEBT entrance Twiss parameters to best match measured wire profiles under a variety of quad settings•Uses solver + online model packages with live machine data input.

phase 3 – chopper functionality (time ∫)SETUP: low current beam, chopper ON DC

AIM: measure individual elements’effect on beam deflection

PROCEDURE: measure beam centroid deflection on MEBT WS near dump & residual transmission on TRAFOs.

X - Y Y-Y’

W/o optical deflection enhancement

with optical deflection enhancement

phase 4 – chopper functionality (time resolved)

SETUP: MEBT+ test bench, full current beam, chopper ON AC

AIM: test time resolved chopper functionality

PROCEDURE: measure intensity of partially chopped beam with Masaki’s detector, chopping efficiency, rise/fall times with beam

Not completely chopped bunch

Transmitted bunch

mm scale, <2ns resolution

DTL commissioning• Transverse commissioning should be easier, if we get the initial conditions right! (all intertank PMQs)

• Set RF point by scanning in phase/amplitude and looking for best match with simulated characteristic curves. Measure output average phase and energy

SteererP.U.

EMQ

SteererP.U.

Steerer , P.U.

EMQ,BCT,Profile

(SEM)

DTL1 DTL2 DTL3

Permanent diagnostics

-50 -40 -30 -20 -10 0 10 20 30 40 50

-60

-50

-40

-30

-20

-10

0

10

20

30

Tank1

110%108%106%104%102%100%98%96%94%92%

Df in (deg)

Df

ou

t (d

eg

)

-50 -40 -30 -20 -10 0 10 20 30 40 508

8.5

9

9.5

10

10.5

11

11.5

12

12.5

Tank1

92%94%96%98%100%102%104%106%108%110%

( )Df in deg

ener

gy (M

eV)

A=108%, 3 points at Dphi=15deg, 0 , 15 deg

input jitter 0.1% dp/p, RF errors, output jitter (measurement error)=0.5deg, 0.05% dp/p Gauss. (1‰ dE/E)

0.5%-0.5deg 1%-1deg

-15 0.55 deg 13keV 1.13deg 15keV

0 0.4deg 4keV 0.44deg 13keV

15 0.45deg 3keV 0.5deg 13keV

DTL commissioning: RF curves

DTL tank1 acceptance studies

-30 -20 -10 0 10 20 30

-0.15

-0.1

-0.05

0

0.05

0.1

0.15

tank1 acceptance

( )Df in deg

()

DE

MeV

Input beam

cut at 10.5MeV output energy

Can be further developed to obtain alternative calculation of longitudinal profiles and/or emittance by measuring beam losses (BCTs, BLMs?)

Tank2, Tank3 Jim’s talk

Software applications desiderata Service applications:

o elogbooko logger

Device specific applications: o Wire scanner o Emittance meter o Beam losses o Feshenko, halo monitor

General purpose tools: o scope applicationo f(t)o histograms o (1-D,2-D?) scan applicationo correlator application

Online model: o automated longitudinal f/A scans and signature matcho comparison of measured and model predicted beam sizes for a variety of

settings, iterative optimisation match to solve for Twiss parameters o orbit correction through steering

basic

complex

Reserve slides

0 10 20 30 40 50 60 70 80 900

50

100

150

200

250

tank2 off

1rms5rms

current (mA)

phas

e sp

read

(deg

)

0 10 20 30 40 50 60 70 80 900

10

20

30

40

50

60

70

80

tank3 off

1rms5rms

current (mA)

phas

e sp

read

(deg

)

TOF for DTL tank2, tank3? Phase spread at the exit of tank2

Phase spread at the exit of tank3

LengthsDTL tanks:4.2m,7.6m,7.4mCCDTL: 2.6-3.3mPIMS modules: 1.3-1.5m (2modules at least for 1‰dE/E)

0 1000 2000 3000 4000 5000 6000 7000 80000

20

40

60

80

100

120

140

160

180

TOF, dphi=1deg, dL=0.3mm

12 MeV

30 MeV

50 MeV

100 MeV

distance bw PUs (mm)

de

lta

E (

ke

V)

-50 -40 -30 -20 -10 0 10 20 30 40 50

-70

-60

-50

-40

-30

-20

-10

0

10

20

30

Tank2

92%94%96%98%100%102%104%106%108%110%

( )Df in deg

(

)D

fo

ut

de

g

-50 -40 -30 -20 -10 0 10 20 30 40 5010

15

20

25

30

35

Tank2

92%94%96%98%100%102%104%106%108%110%

( )Df in deg

Ener

gy (M

eV)

A=103%, 3 points at Dphi=15deg, 0 , 15 deg input jitter 0.025% dp/p, 1deg, RF errors, output jitter (measurement error)=0.5deg, 0.05% dp/p Guass (1‰ dE/E)

0.5%-0.5deg 1%-1deg

-15 0.33 deg 11.5keV 0.55deg 37.2keV0 0.46deg 8keV 0.83deg 34keV

15 0.85deg 8.6keV 1.7deg 34keV

30keV resolution for at least 1.5m distance b/w PUs

-50 -40 -30 -20 -10 0 10 20 30 40 50

-140

-120

-100

-80

-60

-40

-20

0

tank3

92%94%96%98%100%102%104%106%108%110%

( )Df in deg

(

)D

fout

deg

-50 -40 -30 -20 -10 0 10 20 30 40 5035

37

39

41

43

45

47

49

51

53

Tank3

92%94%96%98%100%102%104%106%108%110%

( )Df in deg

Ener

gy (M

eV)

A=104%, 3 points at Dphi=15deg, 0 , 15 deg

input jitter 0.023% dp/p, 0.5deg, RF errors, output jitter (measurement error)=0.5deg, 0.05% dp/p Gauss (1‰ dE/E)

0.5%-0.5deg 1%-1deg

-15 0.76 deg 15.8keV 1.5deg 54.4keV

0 0.46deg 8keV 0.56deg 54.7keV

15 0.85deg 8.6keV 0.48deg 51.5keV

50keV resolution for at least ~2m distance b/w PUs