Diagnostics and commissioning on ERLP

Yuri Saveliev

ASTeC

CONFORM Project: EMMA Design Review Workshop26-28 February 2007, Daresbury Laboratory

ERLP Injector parameters

DC gun voltage 350kV

Bunch charge 0-80pC

Bunch repetition frequency 81.25Mhz

Train length 0-100 s

Train PRF 1-20Hz

Average current in train 6.5mA ( @ 80pC)

Laser pulse duration ~6ps (~25ps with pulse stretcher)

Laser pulse energy 0-40nJ

Laser spot position on cathode variable

Laser beam diameter on cathode 2-6mm FWHM (variable)

Buncher input RF power ~2kW (~70kV peak voltage)

RF kicker power ~200W

ERLP diagnostic beamline

ERLP Diagnostic beamline schematicC

atho

de

Ano

de

GateValve

Ligh

t Box

BPM-01

SOL-01VCOR-01HCOR-01

Buncher

A BFC 1

Tran

sver

seK

icke

r

C

DE

FC 2Dimensions: Survey data (A0-183-11686 dated 14/07/06)

ERLP Injector test beamline v2.5 (29/08/2006)

SOL-02VCOR-02HCOR-02

VCOR-06HCOR-06 YAG-01

3030

50

HSLT-01 VSLT-01

50

-22 200

-59 500

30-16 500

-54 060

-55 400

-18 500

-60 260

-22 700

ANMAG-01

YAG-02

YAG-03 YAG-04

"a"

Sections schematics when looking downstream (i.e. from the gun)

NOTES: 1) Section “B” position coincides with the position of the 1st cell of booster2) Everything downstream SOL-02 will be replaced by the booster

Diagnostic beamline: what we can measure

Bunch charge (Faraday cup)Electron energy (HV PSU voltage]

Laser beam position/size on cathode (direct viewing, virtual cathode)Cathode QE (QE scanner, FC)

Beam steering (YAGs, BPM)Transverse beam size and profile (YAGs)Transverse emittance (V & H slits, pepper pot, YAGs, FC)

[both X and Y; transverse phase space]

Energy spread / spectrum (dipole, YAG, slit, FC-02)[with buncher – correlated and uncorrelated energy spread]

Bunch length / longitudinal profile (RF transverse kicker, YAG)[longitudinal phase space]

Diagnostic beamline: what we need to do

Strategic goals:- gun characterisation at various bunch charges Q;- gun optimisation at Q=80pC (or the highest Q available)

needed for: (i) matching computer simulations and experiment; (ii) projecting the injector behaviour to nominal bunch charge

Beam related tasks …- HV gun electrodes conditioning proper (done; 450kV)- laser pulse stretcher (done; ~25ps)- good laser transverse shape without the pinhole - QE >1% (done; =1.2%)- cathode lifetime - BPM, buncher and RF kicker characterisation (started)- ………

Diagnostic beamline: what we need to do

Beam studies- beam steering/focusing at high Q- beam halo (if any)- solenoid scans (var Q)- transverse emittance at buncher and 1st booster cell (var Q)- energy spread (correlated/uncorrelated) (var Q)- bunch length and longitudinal profile (var Q)- optimal settings for Q=80pC (or the highest available)

Also …- keep an eye on QE and the cathode lifetime- effect of buncher operation on QE- optimisation of laser beam size (time permitted; unlikely though …)

Commissioning problems

Period 1 (21 July – 5 October, 2006)

- conditioning resistor failure- gun not conditioned properly for 350kV operation- gun instability in 260-310kV range of voltages- low and rapidly deteriorating QE (~0.5% max and ~0.1% most of the time)- gun vacuum/current leakage problems after one of the cathode activations

beam studies: ~1 week at 250keV and ~1 week at 350keV

Period 2 (7 January – 3 February, 2007)

- strong field emission from the cathode (due to new wafer ?)- rapidly deteriorating QE (although high initially >1%)- highly non-uniform QE map (due to wafer heating problems)- mechanical failure inside the cathode ball (flap)

beam studies: <2 weeks at <350keV

Quantum efficiency, bunch charge, lifetime

Quantum efficiency:- maximum registered (machine): QE=1.2%- on a stand-alone test system, QE=3.5% has been

achieved Bunch charge:

- maximum registered: Q=9pC (with pinhole) Cathode lifetime:

-no solid data yet, but the lifetime is not good enough anyway (field emission)

0

2

4

6

8

10

0 0.2 0.4 0.6 0.8 1 1.2

Q, pC

y = 0.096 + 9.0345x R= 0.9992

Q,

pC

Laser Att. (#302)

Bunch charge v Laser Att. [#302]Laser: 40.03uJ just before shutter 2 at Laser Att.=1.0 and 100us.

Dipole calibration

0

5

10

15

20

25

240 245 250 255 260

X, mm

y = -271.89 + 1.1275x R= 0.99773

X, m

m

Voltage, kV

DIPOLE CALIBRATION (CRUDE) Data: 28/08/06 Logbook entry #147

Calibration made at 250keV because of Voltage instability at nominal 350keV

Sensitivity with YAG-03 (Section D):1.13mm/keV

Scaling to other energies:

)1(

TdT

d

Scaled to 350keV, the sensitivity is: 0.85mm/keV(Note: theory gives 0.86mm/keV)

Beam steering

Beam steering is far from intuitive because of solenoids

-15

-10

-5

0

5

10

15

-10 -5 0 5 10

VCOR-06 and HCOR-06 @ YAG-01Data #143

V(vcor)V(hcor)

y = 13.837 - 15.886x R= 0.99243

y = -0.044751 + 0.0076056x R= 0.83302

Ve

rtic

al p

osi

tion,

mm

Horizontal position, mm

VCOR-06

HCOR-06

-15

-10

-5

0

5

10

-6 -4 -2 0 2 4 6

VCOR-06 and HCOR-06 @ YAG-02Data #143

V(vcor)V (hcor)

y = -4.8114 - 1.2148x R= 0.99914

y = -5.0806 + 2.0868x R= 0.99847

Ve

rtic

al p

ositi

on,

mm

Horizontal position, mm

VCOR-06

HCOR-06

Solenoids:- Strong correctors :f=24cm at 300G => ~40mrad kick (!) at ~10mm offset- Rotate the beam by ~45o (at ~300G field)

Transverse emittance

350keV; Slit HSLT-01 (“B”) and screen “C”laser spot diameter = 5.2mm (approximately ±2σ)

Q=0.16pC ε = 0.9 mm.mrad (normalised) Q=0.06pC ε = 0.8 mm.mrad (normalised)

320 340 360 380 400 420

200

220

240

260

280

300

320

But: both are overestimated due to image saturation !!!

Energy spread

Only first rough estimates yet …

At 300keV; Q<3pC : E <0.5keV

Bunch length

0

500

1000

1500

2000

2500

3000

0 2 4 6 8 10 12

2027()2114 (P=200)2117 (P=287)2120 (P=347)2123 (P=408)

Inte

nsi

ty ,

arb

. un

its

Position on YAG-03, mm

Transverse profiles of slit "A" images on YAG-03 (#375) at various buncher RF power

HEAD TAIL

P=0.8W

P=146W

P=233W

P=293W

P=354W

0

1

2

3

4

5

6

7

8

0 5 10 15 20 25 30 35

y = 1.1659 + 0.18468x R= 0.98691

Ele

ctro

n en

ergy

E

, ke

V

V0 (kV)

Full width of the slit "A" image on YAG -03 v peak buncher voltage V0Data #375

“Non-conventional” technique (use of dipole and buncher)

Bunch length estimated to be ~23ps(full bunch length) at low bunch charges

ERLP diagnostics schematic

LINAC

BOO

STER

GU

N

SOL-01

H&V-01

H&V-06BPM-01

BUNCHERYAG-01

SOL-02

H&V-02 BPM-02

Q-01

YAG-02 Q-02

BPM-03

H&V-03 Q-03

Q-04

YAG-03

DIP-01

Q-05

DIP-02

YAG-??

FCUP-01

BPM-04H&V-04

Q-06Q-07

Q-08Q-09

DIP-3

Q-10

YAG-04

Q-11 BPM-05H&V-05

Q-12

INJECTOR

OTR-01BPM-01H&V-01

ST1

OTR-02 DIP-01DIP-02

DIP-03Q-01

OTR-03

BPM-02H&V-02

Q-02 Q-03 Q-04

OTR-04

BPM-01DIP-01

BPM-02SEXT-01

OTR-01

ST1 ARC1

ARC1

Q-01

V-01

Q-02

BPM-03

DIP-02

BPM-04

Q-03

V-02

Q-04

OTR-02SEXT-02

BPM-05DIP-03

BPM-06

OTR-01

Q-01Q-02

BPM-01H&V-01

OTR-02

Q-03Q-04

BPM-02H&V-02DIP-01

DIP-02BPM-03V-03

OTR-03

DIP-03

DIP-04Q-05

ST 2ST 2

ARC 2 PLM-01TCM-01

BPM-04H&V-04

BPM-05H&V-05

BPM-01H&V-01

Q-06Q-07

WIGGLER

ST 3ST 3

Q-01Q-02

Q-03Q-04

OTR-01

BPM-02H&V-02

BPM-01DIP-01

BPM-02SEXT-01

OTR-01

Q-01

V-01

Q-02

BPM-03DIP-02

BPM-03Q-03

V-02

Q-04

OTR-02SEXT-02BPM-05

DIP-03BPM-06

ARC 2

ST4

OTR-01Q-01 Q-02

BPM-01H&V-01

Q-03

DUMP-01

Q-04 Q-05

BPM-02H&V-02

OTR-02DIP-01 DIP-02 DIP-03

BPM-01Q-01

Q-02Q-03

OTR-01

DMP

1 m

Note: scale is for guidance only

ERLP SCHEMATIC DIAGRAM

v.0.2 (15/06/2006)extracted from AO-180/10078/E

ERLP diagnostics: Gun to Booster

BOO

STER

GU

N

SOL-01

H&V-01

H&V-06BPM-01

BUNCHERYAG-01

SOL-02

H&V-02 BPM-02SlitVertical

ERLP diagnostics: Booster to Linac

LINAC

BOO

STER

Q-01

YAG-02 Q-02

BPM-03

H&V-03 Q-03

Q-04

YAG-03

DIP-01

Q-05

DIP-02

YAG-??

FCUP-01

BPM-04H&V-04

Q-06Q-07

Q-08Q-09

DIP-3

Q-10

YAG-04

Q-11 BPM-05H&V-05

Q-12

OTR-01BPM-01H&V-01

DIP-03

Twiss parametersEmittance

Slit here ?

Energy spread/spectrumAbsolute energy Buncher gradient / phase(?) setting

Bunch charge

Setting achromaticcondition (Q01-Q05)

Twiss parametersEnergy spread

Setting achromaticcondition (Q10, Q12)

ERLP diagnostics: Linac to Arc 1

LINAC

OTR-02 DIP-01DIP-02

DIP-03Q-01

OTR-03

BPM-02H&V-02

Q-02 Q-03 Q-04

OTR-04

BPM-01DIP-01

BPM-02SEXT-01

OTR-01

Twiss parametersEmittanceDispersion correction

Slit here ?

Energy spread/spectrumAbsolute energy

Bunch charge (?)