Development of a Compact Dielectric-Loaded Test Accelerator at 11.4 GHz* S.H. Gold, a) A.K. Kinkead,...
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Transcript of Development of a Compact Dielectric-Loaded Test Accelerator at 11.4 GHz* S.H. Gold, a) A.K. Kinkead,...
Development of a Compact Dielectric-Loaded Test
Accelerator at 11.4 GHz*
S.H. Gold,a) A.K. Kinkead,b) W. Gai,c) J.G. Power,c) R. Konecny,c) C. Jing,c,d) and A.W. Flifleta)
a) Plasma Physics Division, Naval Research Laboratory, Washington, DC 20375b) Icarus Research, Bethesda, MD 20814
c) Argonne National Laboratory, Argonne, IL 60439d) Euclid TechLabs, Solon, OH 44139
Presented at13th Advanced Accelerator Concepts Workshop
Santa Cruz, CA27 July – 2 August 2008
*DoE Interagency Agreement #DE–AI02–01ER41170
NRL Magnicon Facility
• Magnicon Facility offers a flexible venue for hands-on experiments requiring high power 11.4 GHz radiation, with reasonable work and safety rules and minimal red tape
• Magnicon properties: high power (10–20 MW), adjustable pulse length (200-ns FWHM– 1-µs), repetition rate up to 10 Hz, stable gain, a modest (~0.1%) tuning range, phase stability, and stable operation into resonant loads
• Magnicon facility has been used for two series of collaborative experiments over the past 5 years:
– Sixteen tests of DLA Structures– Eight tests of Active Pulse Compressors
• It is now being used to power a 5-MeV injector, the first stage of a compact test accelerator to study acceleration in DLA structures
Magnicon Facility Schematic
Magnicon
Power Combiner/Splitter Load
5 MeV Injector DLA Structure Spectrometer
X-Band Test Accelerator
Magnicon
Power Combiner/Splitter Load
5 MeV Injector 20 MeV Dielectric-Loaded Accelerator Spectrometer
Accelerator
Section
Focusing
Quads
Cathode
Assembly
Device
under test
X-Band Test Accelerator
ICT YAG
Design Parameters
Energy 5.2 MeVCharge/Bunch >5 pC RF Frequency 11.430 GHzRF Power in ~2 MWQ ~1000Norm.Emittance 3.1 mm mradEnergy Spread ~6%
MatchingQuads
Injector
NRL X-Band Injector
LaB6 Cathode
Accelerator Lab of Tsinghua University 胡源 (Y. Hu, Student), 杜晓福 (X. Du),唐传祥 (Prof. C. Tang), and 林郁正 (Prof. Y. Lin)
Measured Axial Field Profile and PARMELA Results
Temperature Tuning the Injector
Linear Fit
Experimental Data
Cavity filling comparison
0.0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
0.9
1.0
0.0E+00 2.0E-07 4.0E-07 6.0E-07 8.0E-07 1.0E-06
Time (s)
Normalized RF Power
0.E+00
5.E-09
1.E-08
2.E-08
2.E-08
3.E-08
3.E-08
4.E-08
4.E-08
5.E-08
5.E-08
Stored Energy for 1 W drive (J)
Pforward
Wref
W
Injector Cavity Filling Calculation
P forward, P injected, P reflected vs time
-0.2
0.0
0.2
0.4
0.6
0.8
1.0
0.E+00 2.E-07 4.E-07 6.E-07 8.E-07 1.E-06
Time (s)
Normalized RF Power
PforwardPinjectedPreflected
Q0 = 9700
Qe = 1115
= 8.7
1.0E+03
1.0E+04
1.0E+05
1.0E+06
1.0E+07
1.0E+03 1.0E+04 1.0E+05 1.0E+06 1.0E+07
Forward Power (W)
Reflected Power (W)
Conditioning the Injector
y = 0.65x
Pforward
(6 MW)Preflected
ICT
4 mm
(0.5 mA)
Initial Accelerator Operation
Beam Deflection Measurement
~ 7.5
• Injector installed with rf window, gate valve, ICT, YAG, focusing quads, steering magnet
• RF conditioning completed
• Dark current electrons observed; energy of ~3–5 MeV, based on electron range in Al and bending in 1.2 kG magnetic field
• Initial operation with hot cathode at rated rf drive (~2 MW injected) produced ~1 mA, ~3.2 MeV, 4-mm-diam beam
• Low cathode temperature, apparent cathode poisoning limited beam current from LaB6 cathode
• Temperature gradient along 24-cell structure may have limited beam energy
• These problems will be addressed in the near future
Compact Accelerator Summary