Design Considerations for the AWAKE Electron Source

UoM-CI Group Meeting December 2014

Dr Oznur Mete The University of Manchester The Cockcroft Institute of Accelerator Science and Technology

On behalf of our team from The Cockcroft Institute, G. Xia (The University of Manchester) G. Burt, M. Jenkins (The University of Lancaster) C. Welsch (The University of Liverpool) In collaboration with S. Döbert (CERN)

1 Motivation 2 Motivation AWAKE Facts

2013 • Approval of project at CERN including funding proﬁle.

2014-2015 • Design, procurement and installation of the equipment, development of plasma cells. • Modiﬁcation and installation of the beam line and the experimental facility.

2016 • First proton beam to the AWAKE experiment, beam–plasma commissioning. • Beginning taking data

2017 • Installation of the Electron source and beam line. • Delivery and installation of the electron photo-injector, commissioning of the magnetic spectrometer. • More data taking!

International Effort

16 institutions in 9 countries across Europe and Asia. http://awake.web.cern.ch/awake/

3 Motivation PHIN and AWAKE ‣ Design based on the existing PHIN RF gun (Roux 2004, Doebert 2006), ‣ PHIN was installed and commissioned at CERN (Mete 2011), ‣ Houses electron beam diagnostics (transverse beam size, emittance, energy, energy spread, in single-shot and time-resolved manners) (Egger 2010, Olvegard 2012, Mete 2012). ‣ Optimised for CLIC drive beam (long trains of high charge bunches with an intensity stability of quarter of a percent), ‣ Start to end simulations (PARMELA, L.M. Young, 2003) towards the design of an electron gun for AWAKE project.

Speciﬁcations for AWAKE e- beam.

4 Introduction

Deliverable results ‣ On crest phase of the structure for the optimum location, ‣ Emittance compensation in the space charge dominated regime, ‣ Reference settings delivered to transfer line, ‣ Space charge and emittance after acceleration, ‣ Consequences of the phase jitter. Mid-term plans ‣ Triplet for matching and quad scan, ‣ Sensitivity and wide range characterisation studies, ‣ Implementation of CST ﬁeld maps.

5 The layout considered

Incident, Reﬂected Power Bucking Coil Focusing Solenoid Emittance Meter Matching Triplet Corrector Magnets Travelling Wave Structure

BPR Multi-Slit CCD WCM MASKMask FCT

Cathode RF Gun Laser Diagnostics Diagnostics and 0 180 1185 1415 1739 2739 3000 Transfer line

16 New TWS location after

15 16.17 integration considerations. 16.165

14 16.16

16.155 13 16.15 E (MeV) E (MeV) 16.145 12 16.14 11 16.135 16.13 218 219 220 221 222 223 224 10 Phase (o)

9 −300 −250 −200 −150 o Phase ( ) 6 A range about the minimum emittance

3.5 1.4 2820 2820

2800 1.2 2800 3 2780 2780 1 2760 2760 2.5 2740 0.8 2740 (mm)

2720 x 2720 σ (mm mrad) 0.6 2 x,n

ε 2700 2700

Focusing Field (G) 0.4 Focusing Field (G) 2680 2680 1.5 2660 0.2 2660

2640 2640 1 0 0 100 200 300 400 0 100 200 300 400 Distance (cm) Distance (cm)

30 14 2820 2820

2800 12 2800 20

2780 2780 10 10 2760 2760

2740 8 2740

x,y 0 α 2720 (m/rad) 2720

x,y 6 β −10 2700 2700 Focusing Field (G) 4 Focusing Field (G) 2680 2680 −20 2660 2 2660

2640 2640 −30 0 0 100 200 300 400 0 100 200 300 400 Distance (cm) Distance (cm) 7 The reference setting

Magnetic ﬁeld for compensation solenoid is 2744 Gauss.

TWS Exit (2770 mm)

βx/y (m/rad) 6.1/ 6.3

αx/y -0.6 / -0.6

σx/y (μm) 556 / 577

εx/y (mm mrad) 1.6 / 1.7

E(MeV) 16

ΔE (%) 0.3

8 Space Charge Limits

Defocusing space charge term Outward pressure due to rms emittance. 2 0 s ✏n 00 + 0 + K =0 2 r 33 322

1 10 0.1 nC − 0.3 ps 0.2 nC − 0.3 ps 1 nC − 0.3 ps 0.1 nC − 4 ps 0.2 nC − 4 ps 0 1 nC − 4 ps 10 2.33 nC − 4 ps Emittance Dominated

2 2 s ✏n >> s κ

2 −1

σ 10 / βγ 2 n

ε Space Charge Dominated

2 2 −2 ✏n << s 10

−3 10 500 1000 1500 2000 2500 3000 3500 4000 Position (mm) 9 Space Charge Limits

Defocusing space charge term Outward pressure due to rms emittance. 2 0 s ✏n 00 + 0 + K =0 2 r 33 322

Downstream (3500 mm)

Case ε2nβγ / σ2κs

1nC - 0.3ps 0.01 Emittance Dominated

0.2nC - 0.3ps 0.04 2 2 ✏n >> s 0.1nC - 0.3ps 0.02

2.33nC - 4 ps 0.1 Space Charge Dominated 1nC - 4ps 0.2 2 2 ✏n << s 0.2nC - 4ps 0.3

0.1nC - 4ps 0.3

10 Implications of phase jitter on beam dynamics

‣ Error source for both SW and TWS, the klystron, ‣ 2.99855 GHz, 1o corresponds to ~1ps, measured phase jitter in CTF3 ~200fs, ‣ Phase jitter simulations for AWAKE injector; 300fs (1σ) over 100 samples around the on-crest phase (8 hours to simulate).

Incident, Reﬂected Power Bucking Coil Focusing Solenoid Emittance Meter Matching Triplet Corrector Magnets Travelling Wave Structure

BPR Multi-Slit CCD WCM MASKMask FCT

Cathode RF Gun Laser Diagnostics Diagnostics and 0.8 0 180 1185 1415 1739 2739 3000 Transfer line 0.6

0.4

0.2

−0.2

Random Error −0.4

−0.6

−0.8 0 20 40 60 80 100 Number of Shots 11 Implications of phase jitter on beam dynamics

30 60 µ = 1.6405, σ = 0.00013413 µ = 0.55537, σ = 0.00034562 20 40

Counts 10 Counts 20

0 0 1.64 1.6402 1.6404 1.6406 1.6408 1.641 0.554 0.5545 0.555 0.5555 0.556 0.5565 0.557 0.5575 (mm mrad) (mm) εx σx

30 30 µ = 2.4041, σ = 0.02542 µ = 3.2806, σ = 0.015207 20 20

Counts 10 Counts 10

0 0 2.3 2.35 2.4 2.45 2.5 2.55 3.22 3.24 3.26 3.28 3.3 3.32 3.34 3.36 (1e−6m) (ps) εz σz

60 40 µ = 16.1651, σ = 0.00016907 µ = 0.0025808, σ = 4.6882e−05 30 40 20

Counts 20 Counts 10

0 0 16.1644 16.1646 16.1648 16.165 16.1652 16.1654 16.1656 16.1658 2.4 2.5 2.6 2.7 2.8 −3 E (MeV) ∆ E/E (%) x 10

12 Implications of phase jitter on beam dynamics

Reference Parameter μ300fs σ300fs Error Value

εx 1.6 mm mrad 1.6 mm mrad 0.13e-3 mm mrad 0.5 nm/deg

σx 556 μm 555 μm 0.3 μm 1 μm/deg

σz 3.3 ps 3.3 ps 15 ns 50 ns/deg

E 16.15 MeV 16.16 MeV 170 keV 600 keV/deg

σE 0.3% 0.3% 0.005% 0.02 %/deg

13 Matching Triplet

Boundary condition Injector outputs around 10 at triplet exit. 9 equilibrium. 8 7 3200 6 3100 5 (mm mrad) 3000 4 x,n ε 3 2900

2 2800

1 2700

0 2600 0 100 2500 200 3200 Distance (cm) 2400 300 3100 400 2300 3000

2900 3 2800

2.5 2700

2600 2 2500

1.5 2400

(mm) x

σ 2300 1 300 250 50 200 0.5 150 40 100 50 Distance (cm) 0 30 0

20 3200 10

x,y 3100 α 0 −10 3000

−20 2900

−30 2800

−40 2700 − 50 2600 0 100 32002500 200 Distance (cm) 31002400 300 400 23003000 2900 90 2800 80 2700 70 2600 60 2500 50 2400

(m/rad) 40 2300 x,y

β 30 400

20 300 200 10 100 Distance (cm) 0 0

14 Summary

‣ Extensive PARMELA simulations were performed to optimise the PHIN photo injector to provide the baseline settings for AWAKE electron beam.

‣ A TWS and a quadrupole triplet were added to the model,

21.3

21.25

21.2

21.15 2 Simulation Interpolation ‣ TWS was optimised for the on-crest phase, and emittance compensation21.1 Energy21.05 (MeV)

1.5 −160 21 −162 20.95 − (mm mrad) 164

x,n 20.9 ε −166 was ensured after acceleration, 1 −180 −168 −175 −170 −170 Phase ( −172 o ) −165 0.5 0 −174 −160 50 100 −176 Distance150 (cm) 200 −178 250 300 −180 ‣ PIC parameters were studied, associated errors were estimated,

‣ A set of reference speciﬁcations were determined aimed for the baseline

electron beam, 0.8 0.6

0.4

0.2

−0.2 ‣ Implications of the RF phase jitter were studied. Random Error −0.4 −0.6

−0.8 0 20 40 60 80 100 Number of Shots ‣ Matching between the injector and the transfer line was studied by using a quadrupole triplet,

‣ Various solutions for several working points in the “region of interest” were calculated that are satisfying the baseline.

15 OUTLOOK (2015/Q1)

‣ Quad scan after TWS,

• Simulate with and w/o space charge effect,

• A method of scaling if necessary (determining transfer matrix with space charge etc.). ‣ Comparison with the theoretical curve for paraxial envelope, ‣ Sensitivity to initial parameters (laser, beam distribution etc.), ‣ Parameter scan in the range of interest. ‣ Results with real ﬁeld map - should be double checked asap.

16 References

‣ L. M. Young and J. Billen, in Proceedings of the 20th Particle Accelerator Conference, Portland, OR, 2003 (IEEE, New York, 2003).

‣ R. Roux, Design of a RF Photo-Gun, CARE Note-2004-034-PHIN, (2004).

‣ S. Doebert, Integration of PHIN RF GUN into the CLIC Test Facility, CLIC-NOTE-689 (2006).

‣ O. Mete et al., Study and characterisation of a novel photo injector for the CLIC drive beam, PhD Thesis EPFL-5020 (2011).

‣ D. Egger et al., The Status of the design of the PHIN spectrometer line diagnostics for time resolved energy measurements and ﬁrst results from 2009, CTF3-Note-009 (2010).

‣ M. Olvegard et al., High intensity proﬁle monitor for time resolved spectrometry at the CLIC Test Facility 3, NIMA 683 29-39 (2012).

‣ O. Mete et al., Production of long bunch trains with 4.5μC total charge using a photoinjector, PRSTAB 15, 022803 (2012).