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!