AAC10 WG5 SummaryAAC10 WG5 Summary““Beam and Radiation Generation, Monitoring and ControlBeam and Radiation Generation, Monitoring and Control””

Mike Church, Kiyong KimAnnapolis, June 13 - 19

WG5 SummaryWG5 Summary

• WG5 touched on a broad set of topics

• Cathodes and guns – 2 sessions

• Radiation generation – 2 sessions + 1 joint with WG1/4

• Diagnostics – 2 sessions

• Beam control and dynamics – 3 sessions

• 33 WG orals + 15 posters + 2 plenaries

• strong student participation – 18 student presentations (oral and/or poster)

I will present some highlights, put cannot adequately cover all the presentations. (My apologies to those who get short shrift.)

Cathodes and guns

SRF (J. Lewellen)DC (J. Zhou)RF (C. Neumann)

Guns

Diamond amplified (I. Ben-Zvi)Photocathode (P. Musumeci, K. Nemeth, M. Uesaka)Thermionic (L. Ives)

Cathodes

I. Ben‐Zvi

The Diamond Amplified Photocathode:The Diamond Amplified Photocathode:Robust, high QE, low thermal emittance, highRobust, high QE, low thermal emittance, high--currentcurrent

LaserPhotocathode

Metal coating

RF cavity

Hydrogenated surface

Primary beam

-10kV

Diamond

Secondary beam

Gap

15 A/cm2, gain of 100’s measured. Expected <0.05 eV thermal emittance.

Detailed simulations by Tech‐X.Compared to experiments.

1st observed beam

High Current Density Thermionic CathodesHigh Current Density Thermionic CathodesLawrence Ives Lawrence Ives –– Calabazas Creek ResearchCalabazas Creek Research

Controlled porosity reservoir cathodes (CPCR) offer high current densities with long life

Uniform Porosity

Control ofBarium Diffusion

Calculated lifetime = 32,000 hours @ 50 A/cm2

Improved Performance

Barium Reservoir

Beam Imaging of an Elliptic Electron Gun Beam Imaging of an Elliptic Electron Gun atat 900 V/26 900 V/26 mAmA, 1 , 1 micromicro--perveanceperveance –– Jing Zhou, Beam Power TechnologyJing Zhou, Beam Power Technology

Description OMNITRAK Experiment

Horizontal beam width, a 5.3 mm 5.3 mm

Vertical beam width, b 2.6 mm 2.7 mm

Aspect Ratio, a/b 2.0 2.0

Comparison with theory

Applicable for L-band elliptic beam klystrons or elliptic electron sources

Beam Control and Diagnostics

UMER (R. Kishek, S. Bernal, B. Beaudoin, T. Koeth, K. Fiuza)Adiabatic Thermal Beams (C. Chen)

Beam Dynamics

Emittance Exchange (P. Piot, J. Power, B. Carlston, D. Xiang, J. Ruan)CSR Suppression (M. Fedurin)Beam Compression with THz (J. Moody)

Beam Control

Philippe Piot

LongitudinalLongitudinal phase space manipulation at AWA using the phase space manipulation at AWA using the EEX EEX beamline beamline ––John Power ANLJohn Power ANL

6mm

R = 4

Increasing the transformer ratio with a ramped bunch

CL

WITNESS BUNCH

DRIVEBUNCH

0 0.5 1 1.51

0.5

0

0.5

1

z (cm)

Wz

(MV

/m/n

C)

.W-

W+

(Maximum energy gain behind the drive bunch)(Maximum energy loss inside the drive bunch) < 2R = W+

W- = for gaussian drive

Longitudinal ramped beam accomplished with EEX line and transverse mask using upgraded AWA (30 MeV)

Laser assisted emittance exchange – Dao Xiang, SLAC

Phase space after interaction with the TEM10 laser

Before exchange After exchange

Soft x-ray FEL at 1.5 nm

E=1.2 GeV; Ls=15 m; Np=3*1011

Hard x-ray FEL at 0.15 nmE=3.8 GeV; Ls=30 m; Np=5*1010

Phase Space Partitioning Phase Space Partitioning (Bruce Carlsten, LANL)(Bruce Carlsten, LANL)

Phase space from a photoinjector is very cold – overall volume is more than sufficient for our needs:

“typical” photoinjector at 0.5 nC:εx ∼ 0.7 mm mrad εy ∼ 0.7 mm mradεz ∼ 1.4 mm mrad

our needs:εx ∼ 0.15 mm mrad εy ∼ 0.15 mm mradεz ∼ 100 mm mrad

volume ∼ 0.7 (µm)3 volume ∼ 2.3 (µm)3

Electron Injector

Linear Accelerator

Bunch Compressor

UndulatorX-rays Beam

Electron Beam Dump

Original MaRIE 50Original MaRIE 50--keV XFEL Baseline ConceptkeV XFEL Baseline Concept

EEX Prebuncher IdeaEEX Prebuncher Idea

Kishek, et al., SpaceKishek, et al., Space--Charge Dominated Studies at UMERCharge Dominated Studies at UMER

Goal: To study space charge physics and verify models preservation of beam quality

Status: Recently exceeded 1000 turns for a beam with tune shift of 1.0 using longitudinal focusing

0.6 mA beam,Tune Shift > 1.0>1000 Turns

0 50 100 150 200-0.6

-0.5

-0.4

-0.3

-0.2

-0.1

0.0

0.1

Bea

m C

urre

nt (m

A)

Time (µs)

Recent and Ongoing Work:

• Longitudinal: Focusing / Edge Erosion / Waves / Solitary Waves

• Transverse: Beam Halo / Ring Resonances / Lattice Function Measurements

• Novel Diagnostics: Tomography / Halo Core-masking / DC Beam detection

Capability developed for basic characterization (chromaticity, momentum compaction and dispersion) over 4 turnsAll injected beams, 0.6 mA Ibeam 100 mA at 10 keV, amply exceed Laslett tune shift limitLinear (1st and 2nd) betatron resonances observed over 5-100 turnsExploring beam-current dependence of betatron and dispersion functions, coherent tune, and momentum compaction

TransverseTransverse Beam Physics in UMER Beam Physics in UMER –– Santiago BernalSantiago Bernal

5.0 6.0 7.0 8.05.0

6.0

7.0

8.0

Horizontal TuneVe

rtic

al T

une

60%

50

40

30

20

10

0

Fractional transmitted currentof 6.0 mA beam at 20th turn as a function of bare tunes. Linear resonance bands visible

Dynamics in adiabatic thermal Dynamics in adiabatic thermal beams beams –– Chiping ChenChiping Chen

KV beam

Adiabatic thermal beam

AAC2010 C. Chen and H. Wei, submitted to PRL (2010)

• Adiabatic thermal beam is an important state of high-brightness beams.

Samohvalova, et al., Phys. Plasmas (2007) and (2009)Zhou et al., Phys, Plasmas (2008)

• Theoretic predictions are supported by experimental measurements at UMER and Spring-8.

Adiabatic expansion (Bernal, et al., PRST-AB, 2002)Density profile (Bernal, et al,. PRST-AB, 2002; Tagawa, et al., PRST-AB, 2007)

• Adiabatic thermal beams have regular (non-chaotic) phase space and narrow nonlinear resonances.

• Promising approach to controlling beam halo and loss

Radiation generation

Compton scattering (F. Albert)Gamma-ray

Compton scattering (T. Natsui, F. Albert)Betatron radiation (S. Kneip, Joint WG)Laser-driven undulator (F. Gruner, Joint WG)

X-ray

Two-stream instability (K. Bishofberger)Smith-Purcell (P. Piot)Gyrotron (M. Glyavin)IFEL (S. Tochitsky)Corrugated Plasma (A. Pearson)

THz

0 2 4 6 8 10 12 14 16 181

10

100

1000

elec

tric

field

stre

ngth

[kV

/m]

longitudinal position [cm]

30 GHz700 GHz

1 THz

0 200 400 600 800 10000

1

2

3

4

gain

[dB

/cm

]

driving frequency [GHz]

30 GHz130 GHz

400 GHz 800 GHz

Bishofberger: Terahertz Generation Utilizing the Two‐Stream Instability

PIC simulations show excellent bunching of low‐energy beams (~20 keV) through controlled growth of the two‐stream instability.

A dipole merges two separate electron beams; a solenoid (not shown) allows them to co‐propagate. NO STRUCTURES NEEDED!

This device can be used as an oscillator (∆v‐dependent) or amplifier (from below 30 GHz to above 1 THz). Bandwidth is below 1%.

Gain/length is independent of frequency and agree with theory. At a single ∆v, gain bandwidth is nearly a full decade of frequencies.

Several options for radiating a portion of the kW‐level beam power have been analyzed, and work on this aspect continues.

Example simulation illustrating bunching

30 GHz and 1 THz haveequal gain lengths

Large bandwidth aroundcentral frequency.

Kip Bishofberger

Philippe Piot

A series of pulsed THz generators (gyrotrons) with a pulse magnet (40T)has been designed, constructed and tested.

The frequencies up to 1.3 THz and the output power up to 5 kW at 1 THzwas obtained. ( 50 microsecond pulses, 1 pulse/minute)

The possibility of long pulse (1 ms) operation and excitation of the second and third harmonic has been demonstrated.

The projects of pulsed gyrotron with high repetition rate and CW gyrotron, based on experimental test of pulse tubes are under investigation.

Powerful Powerful TerahertzTerahertz GyrotronsGyrotrons

Mikhail Glyavin

Institute of Applied Physics Russian Academy of ScienceNizhny Novgorod, Russia

UCLAUCLA

HighHigh--power THz radiation power THz radiation sourcesourceSergei TochitskySergei Tochitsky

0.5-1.5 THz

2-m long undulator

8-12 MeV

0.01-1 kW

1-m long undulator

10 MW

Chicane

Single-pass amplification

1.5-3 THz

Optical klystron HGHG

3-9 THz

Pulses with a peak power >1 MW cover the spectral range from 0.5 to 9 THz.

118.6 µm

170 µm

57 µm

39.5 µm

Beam diagnostics

ODR (A. Lumpkin)

THz EOS(C. Scoby, M. Helle, J. van Tilborg)

CSR (J. Thangaraj)

Non-intercepting

OTR (COTR, IOTR) (R. Fiorito, A. Lumpkin)

Halo imaging (H. Zhang, R. Fiorito)

Intercepting

Alex Lumpkin

Alex Lumpkin

Bandwidth Mixing X-FROG (BMX-FROG) for the measurement of ultra-short electron beams

• Utilizes full spectrum sum frequency generation to measure ultrashort bunches.• In the presence of the electron beam’s electric field, the EO crystal induces a

rotation in the polarization and frequency shift of the probe laser pulse.• Second harmonic crystal is used to cross-correlate resulting pulse with gate. The

second harmonic pulse is then analyzed by an imaging spectrometer to produce a spectrally resolved cross-correlation. (BMX-FROG).

• The beam profile can be reconstructed (in principle) from the resulting image.

Imaging Spectrometer

EO Crystal

Cross Polarizers

2nd HarmonicCrystal

laser pulse

e‐ beam

Delay

X‐FROG

Michael Helle NRL/Georgetown U.

LOASIS diagnostic: EOS-induced optical sidebands~100 THz bandwidth for few-fs LPA beams

EOS beyond laser bandwidth limit• Narrow-bandwidth probe• THz-induced sidebands

Pros/cons

• Single-shot • No laser limit on resolution/bandwidth• 0-100 THz coverage (few-fs beams)• “Practical” diagnostic (fiber integration)• Spectrometer: lose phase information• Weak sidebands signal

EOS-induced optical sidebandsreplica of ebeam/THz pulse

Etotal(ω0+Ω) ~ ETHz(Ω)

Jeroen van Tilborg

WG5 SummaryWG5 Summary

• We declare AAC10 WG5 a success!

• Sessions were well attended with plenty of open discussion.

• I personally learned a lot and met plenty of new people.

• Thanks to the rest of the organizing committee, and thanks to all contributors!