X-Band High Gradient Linacs. Sami G. Tantawi For the SLAC team and collaborators

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1 X-Band High Gradient Linacs Sami G. Tantawi For the SLAC team and collaborators

2 Acknowledgment The work being presented is due to the efforts of V. Dolgashev, L. Laurent, F. Wang, J. Wang, C. Adolphsen, D. Yeremian, J. Lewandowski, C. Nantista, J. Eichner, C. Yoneda, C. Pearson, A. Hayes, D. Martin, R. Ruth, S.Pei, Z. Li, J. Neilson SLAC T. Higo and Y. Higashi, et. al., KEK W. Wuensch et. al., CERN R. Temkin, et. al., MIT W. Gai, et. al, ANL J. Norem, ANL G. Nusinovich et. al., University of Maryland S. Gold, NRL

3 Outline Introduction and Motivations Collaborative Experimental Research at X-Band Basic Physics experiments varying the structure geometry Material Studies, varying the materials Development of new types of structures Standing-wave Accelerator structures Photonic-band gap structures Dielectric structures Multi-frequency structures Theory Applications to Medical proton linacs Future Plans and Conclusions

4 The Challenge What gradient can be reliably achieved using warm technology? The original, optimistic view (PAC 1986) : E. Tanabe, J. W. Wang and G. A. Loew, Voltage Breakdown at X-Band and C-Band Frequencies, : The authors report experimental results showing that the Surface Electric Field limit at 9.3 GHz (X-Band) exceeds 572 MV/m in pulses of up to 4.5 microseconds Results predict an on-axis gradient of at least 250 MV/m Reality sets in (by 2001): The operating limit determined by experiments on the NLC Test Accelerator showed that high gradient accelerator structure operating at X-band would not survive long term operation without computer/feedback protection and the breakdown rate above 65 MV/m can not be tolerated for a collider application. The challenge: we wish to understand the limitations on accelerator gradient in warm structures Our goal is to push the boundaries of the design to achieve: Ultra-high-gradient; to open the door for a multi-tev collider High rf energy to beam energy efficacy, which leads to an economical, and hence feasible designs Heavily damped wakefield

5 International Collaboration on High Gradient Research KEK CERN SLAC INFN Cockcroft NRL

6 Collaborations It was recognized early that such a study requires us to harness the national and international resources and infrastructures. Hence, we created a national collaboration which comprises: SLAC, NRL, MIT, University of Maryland and ANL, University of Colorado, SBIR companies, and others. Also, we have an international collaboration which includes: SLAC, CERN, KEK, and INFN, Frascati, Cockcroft Institute CTF3 Collaboration/CLIC, which is an international effort with great effect on high gradient research This effort which have a focus on the basic physics of high gradient accelerator is young.

7 Motivations Our collaborations have vitalized research to study the basic physics associated with the limits of room temperature linacs This lead to new advances in the state of the art including: a new optimization methodology for accelerator structure geometries, An ongoing research on alternate and novel materials. New types and novel structures. Advances in the theoretical modeling of the breakdown phenomenon. In addition to colliders, other applications include compact Inverse Compton Scattering gamma ray sources for national security applications, compact proton linacs for cancer therapy, low cost, high-repetition-rate X-ray FELs and dynamic, short-period, large-aperture RF undulators. Research on the basic physics of high-gradient, high frequency accelerator structures and the associated RF/microwave technology are essential for the future of discovery science, medicine and biology, energy and environment, and national security.

8 Research and Development Plan

single cell traveling-wave accelerator structures single-cell standing-wave

9 Experimental Studies Basic Physics Experimental Studies Single and Multiple Cell Accelerator Structures (with major Frscati, KEK and CERN contributions) single cell traveling-wave accelerator structures single-cell standing-wave accelerator structures Pulsed heating experiments Full Accelerator Structure Testing

10 High Power Tests of Single Cell Standing Wave Structures Low shunt impedance, a/lambda = 0.215, 1C-SW-A5.65-T4.6-Cu, 5 tested KEK=#1 KEK-#4 Frascati-#2 Low shunt impedance, TiN coated, 1C-SW-A5.65-T4.6-Cu-TiN-KEK-#1, 1 tested Three high gradient cells, low shunt impedance, 3C-SW-A5.65-T4.6-Cu, 2 tested KEK-#1 KEK-#2 High shunt impedance, elliptical iris, a/lambda = 0.143, 1C-SW-A3.75-T2.6-Cu-SLAC-#1, 1 tested High shunt impedance, round iris, a/lambda = 0.143, 1C-SW-A3.75-T1.66-Cu-KEK-#1, 1 tested Low shunt impedance, choke with 1mm gap, 1C-SW-A5.65-T4.6-Choke-Cu, 2 tested SLAC-#1 KEK-#1 Low shunt impedance, made of CuZr, 1C-SW-A5.65-T4.6-CuZr-SLAC-#1, 1 tested Low shunt impedance, made of CuCr, 1C-SW-A5.65-T4.6-CuCr-SLAC-#1, 1 tested Highest shunt impedance copper structure 1C-SW-A2.75-T2.0-Cu-SLAC-#1, 1 tested Photonic-Band Gap, low shunt impedance, 1C-SW-A5.65-T4.6-PBG-Cu-SLAC-#1, 1 tested Low shunt impedance, made of hard copper 1C-SW-A5.65-T4.6-Clamped-Cu-SLAC#1, 1 tested Low shunt impedance, made of molybdenum 1C-SW-A5.65-T4.6-Mo-Frascati-#1, 1 tested Low shunt impedance, hard copper electroformed 1C-SW-A5.65-T4.6-Electroformed-Cu-Frascati-#1, 1 tested High shunt impedance, choke with 4mm gap, 1C-SW-A3.75-T2.6-4mm-Ch-Cu-, 2 tested SLAC-#1 KEK-#1 High shunt impedance, elliptical iris, ultra pure Cu, a/lambda = 0.143, 1C-SW-A3.75-T2.6-6NCu-KEK-#1, 1 tested High shunt impedance, elliptical iris, HIP treated, a/lambda = 0.143, 1C-SW-A3.75-T2.6-6N-HIP-Cu-KEK-#1, 1 tested High shunt impedance, elliptical iris, ultra pure Cu,, a/lambda = 0.143, 1C-SW-A3.75-T2.6-7N-Cu-KEK-#1, 1 tested Low shunt impedance, made of soft CuAg, 1C-SW-A5.65-T4.6-CuAg-SLAC-#1, 1 tested High shunt impedance hard CuAg structure 1C-SW-A3.75-T2.6-LowTempBrazed-CuAg-KEK-#1, 1 tested High shunt impedance soft CuAg, 1C-SW-A3.75-T2.6-CuAg-SLAC-#1, 1 tested High shunt impedance hard CuZr, 1C-SW-A3.75-T2.6-Clamped-CuZr-SLAC-#1, 1 tested High shunt impedance dual feed side coupled, 1C-SW-A3.75-T2.6-2WR90-Cu-SLAC-#1, 1 tested Now 30 th test is ongoing, single feed side coupled 1C-SW-A3.75-T2.6-1WR90-Cu-SLAC-#1

6-Cu- KEK-#2 A special structure was built and processed (with best cleaning and

11 Surface processing Dr. Yasuo Higashi and Richard Talley assembling Three-C-SW- A5.65-T4.6-Cu- KEK-#2 A special structure was built and processed (with best cleaning and surface processing we can master) at KEK and hermetically sealed, then assembled at SLAC at the best possible clean conditions High Gradient Structures--AAC 2010 Page 11

12 Two structures #1 processed normally and #2 processed similar to superconducting accelerator structures The near perfect surface processing affected only the processing time. The second structure processed to maximum gradient in a few minutes vs a few hours for the normally processed structure.

13 Pure Copper studies Accelerator structures manufactured with different grades of copper purity Accelerator structures manufactured by different laboratories ulseêmeterd Normal copper aêl=0.143, t=2.6mm, SLAC-Ò1 aêl=0.143, t=2.6mm, 6N-HIP-KEK-Ò1 aêl=0.143, t=2.6mm, 7NKEK-Ò1 BreakdownProbability@1ê êpulseêmeterd aêl=0.215, t=4.6mm, Frascati-Ò aêl=0.215, t=4.6mm, KEK-Ò2 aêl=0.215, t=4.6mm, KEK-Ò

14 Geometrical Studies Three Single-Cell-SW Structures of Different Geometries 1)1C-SW-A2.75-T2.0-Cu 2) 1C-SW-A3.75-T2.0- Cu 3) 1C-SW-A5.65-T4.6-Cu 3 2

15 Geometrical Studies Different single cell structures: Standing-wave structures with different iris diameters and shapes; a/λ=0.215, a/λ=0.143, and a/λ= aêl=0.105, t=2.0mm, SLAC-Ò1 aêl=0.143, t=2.6mm, SLAC-Ò1 aêl=0.215, t=4.6mm, KEK-Ò4 aêl=0.105, t=2.0mm, SLAC-Ò1 aêl=0.143, t=2.6mm, SLAC-Ò1 aêl=0.215, t=4.6mm, KEK-Ò Peak Magnetic BreakdownProbability@1êpulseêmeterD BreakdownProbability@1êpulseêmeterD aêl=0.105, t=2.0mm, SLAC-Ò1 aêl=0.143, t=2.6mm, SLAC-Ò1 aêl=0.215, t=4.6mm, KEK-Ò Peak Electric m Global geometry plays a major role in determining the accelerating gradient, rather than the local electric field Peak Pulse CD aêl=0.105, t=2.0mm, SLAC-Ò1 aêl=0.143, t=2.6mm, SLAC-Ò1 aêl=0.215, t=4.6mm, KEK-Ò4

16 Geometrical Studies Different single cell structures: Standing-wave structures with different iris diameters and shapes; a/λ=0.215, a/λ=0.143, and a/λ=0.105, and a/λ=0.143round iris aêl=0.105, t=2.0mm, SLAC-Ò1 aêl=0.143, t=2.6mm, SLAC-Ò1 aêl=0.215, aêl=0.215, aêl=0.143, t=4.6mm, t=4.6mm, t=1.66mm, KEK-Ò4 KEK-Ò4 KEK-Ò1 aêl=0.105, t=2.0mm, SLAC-Ò1 aêl=0.143, t=2.6mm, SLAC-Ò1 aêl=0.215, t=4.6mm, KEK-Ò4 aêl=0.215, aêl=0.143, t=4.6mm, t=1.66mm, KEK-Ò4 KEK-Ò Peak Magnetic Field@kAêmD BreakdownProbability@1êpulseêmeterD BreakdownProbability@1êpulseêmeterD BreakdownProbability@1êpulseêmeterD BreakdownProbability@1êpulseêmeterD aêl=0.105, t=2.0mm, SLAC-Ò1 aêl=0.143, t=2.6mm, SLAC-Ò1 aêl=0.215, aêl=0.215, t=4.6mm, t=4.6mm, KEK-Ò4 KEK-Ò4 aêl=0.143, t=1.66mm, KEK-Ò Peak Electric Peak Electric D Peak Peak Pulse Pulse CD CD Global geometry plays a major role in determining the accelerating gradient, rather than the local electric field. aêl=0.105, aêl=0.105, t=2.0mm, t=2.0mm, SLAC-Ò1 SLAC-Ò1 aêl=0.143, aêl=0.143, t=2.6mm, t=2.6mm, SLAC-Ò1 SLAC-Ò1 aêl=0.215, t=4.6mm, KEK-Ò4 aêl=0.215, aêl=0.143, t=4.6mm, t=1.66mm, KEK-Ò4 KEK-Ò1

17 Pulse Length Dependence Peak Pulse Heating correlate better than peak magnetic field t Pulsed Temp Rise Typical gradient (loaded) as a function of time. aêl=0.143, t=1.66mm, KEK-Ò1--200ns aêl=0.143, t=1.66mm, KEK-Ò1--85ns aêl=0.143, t=1.66mm, KEK-Ò1--300ns aêl=0.143, t=1.66mm, KEK-Ò1--200ns aêl=0.143, t=1.66mm, KEK-Ò1--85ns aêl=0.143, t=1.66mm, KEK-Ò1--300ns Peak Magnetic BreakdownProbability@1êpulseêmeterD BreakdownProbability@1êpulseêmeterD aêl=0.143, t=1.66mm, KEK-Ò1--200ns aêl=0.143, t=1.66mm, KEK-Ò1--85ns aêl=0.143, t=1.66mm, KEK-Ò1--300ns Peak Electric Field@MVêmD Peak Pulse CD aêl=0.143, t=1.66mm, KEK-Ò1--200ns aêl=0.143, t=1.66mm, KEK-Ò1--85ns aêl=0.143, t=1.66mm, KEK-Ò1--300ns

18 Outline Introduction and Motivations Collaborative Experimental Research at X-Band Basic Physics experiments varying the structure geometry Material Studies, varying the materials Development of new types of structures Standing-wave Accelerator structures Photonic-band gap structures Dielectric structures Multi-frequency structures Theory Applications Future Plans and Conclusions

19 Material Testing Experimental and theoretical evidence points to the magnetic field as an important factor in determining the ultimate gradient of a given structure. Magnetic field can be responsible for: Geometrical effects Effective field enhancement Secondary effects due to gas release at high magnetic field points. Surface fatigue can explain the low statistics phenomena of breakdown; why a breakdown occurs every million pulses. Surface fatigue is particularly important in areas where peak magnetic field can cause damage such as wakefield damping areas.

Material Testing ( Pulsed heating experiments) Special cavity has been

Ε SEM Images Inside Copper Pulse Heating Region ΤΕ 013 λικε µοδε Η

for wakefield damping Recent theoretical work also indicate that fatigue and

$Metallography: Intergranular fractures 500X αξισ Q 0 = ~44,000 (Cu, room$

20 Material Testing ( Pulsed heating experiments) Special cavity has been designed to focus the magnetic field into a flat plate that can be replaced. Ε SEM Images Inside Copper Pulse Heating Region ΤΕ 013 λικε µοδε Η Economical material testing method Essential in terms of cavity structures for wakefield damping Recent theoretical work also indicate that fatigue and pulsed heating might be also the root cause of the breakdown phenomenon Metallography: Intergranular fractures 500X αξισ Q 0 = ~44,000 (Cu, room temp.) material sample r = 0.98 TE 01 Mode Pulse Heating Ring Max Temp rise during pulse = 110 o C

21 Hardness Test Value Some of Pulse Heating Samples RF Tested Annealed Copper with large grain shows crystal pattern because damage is different for each crystal orientation 45 Cu101 (SLAC) KEK3 (KEK) HIP2 (KEK) HIP1 (KEK) CuZr2-2 (CERN) 54?? CuCr101 (SLAC) Single Crys Cu (KEK) E-Dep. Cu (KEK) AgPCu (KEK) CuZr3-2 (CERN) CuAg5 (SLAC) CuAg1 (KEK) CuCr102 (SLAC) 3/3/2009 HG workshop, Mar

22 Breakdown and pulsed heating effects on an standing wave accelerator structure iris Photo John Van Pelt

23 Test of a Vacuum Brazed CuZr and CuCr Structures BreakdownProbab bility@1êpulseêmeterd Normal copper aêl=0.215, t=4.6mm, Frascati-Ò2 aêl=0.215, t=4.6mm, CuZr-SLAC-Ò1 aêl=0.215, t=4.6mm, CuCr-SLAC-Ò1 High Gradient Structures--AAC 2010 Page 23

materials without the need to develop all the necessary technologies for bonding and brazing them.

24 Clamped Structure Diffusion bonding and brazing of copper zirconium are being researched at SLAC. Clamping Structure for testing copper alloys accelerator structure The clamped structure will provide a method for testing materials without the need to develop all the necessary technologies for bonding and brazing them. Once a material is identified, we can spend the effort in processing it. Furthermore, it will provide us the opportunity to test hard materials without annealing which typically accompany the brazing process

25 Test of Hard Copper Hard Copper showed an observable improvements of annealed brazed structures 10 0 Clamped Structure with Hard Copper cells BreakdownProbability@1êpu ulseêmeterd aêl=0.215, t=4.6mm, Frascati-Ò2 aêl=0.215, t=4.6mm, Clamped-SLACÒ1 High Gradient Structures--AAC 2010 Page 25

26 Experiments at cryo temperatures Refrigerator head Accelerating structure RF in Solid model: David Martin, 10 January 2011

27 Outline Introduction and Motivations Collaborative Experimental Research at X-Band Basic Physics experiments varying the structure geometry Material Studies, varying the materials Development of new types of structures Standing-wave Accelerator structures Photonic-band gap structures Dielectric structures Multi-frequency structures Theory Applications Future Plans and Conclusions

28 Yet Another Finite Element Code Motivated by the desire to design codes to perform Large Signal Analysis for microwave tubes (realistic analysis with short computational time for optimization) study surface fields for accelerators the need of a simple interface so that one could play A finite element code written completely in Mathematica (then translated to C++) was realized. To our surprise, it is running much faster than SuperFish or Superlance The code was used with a Genetic Global Optimization routine to optimize the cavity shape under surface field constraints 0.6 Surface field penalty function /1/

29 Iris shaping for Standing-Wave π-mode structures Shunt Impedance 83 MΩ/m Quality Factor 8561 Peak E s /E a 2.33 Peak Z 0 H s /E a 1.23 Shunt Impedance 104 MΩ/m Quality Factor 9778 Peak E s /E a 2.41 Peak Z 0 H s /E a 1.12 Shunt Impedance 102 MΩ/m Quality Factor 8645 Peak E s /E a 2.3 Peak Z 0 H s /E a 1.09 Shunt Impedance 128 MΩ/m Quality Factor 9655 Peak E s /E a 2.5 Peak Z 0 H s /E a 1.04 a/λ=0.14 a/λ=0.1 Magnetic Field Distance Along the surface Shape optimization reduces magnetic field on the surface, and hence, we hope to improve breakdown rate with the enhanced efficiency

New Accelerator Architecture for Standing wave accelerator

This is proposed for an efficient high gradient linac for

If one let go of the restrictions imposed by wake fields,

30 New Accelerator Architecture for Standing wave accelerator structures withy a combined damping and feeding. This is proposed for an efficient high gradient linac for application to a warm collider. If one let go of the restrictions imposed by wake fields, the RF distribution system and cell feeding could be done with much more simpler structure. Jeff Neilson

31 New Accelerator Architecture for Standing wave accelerator structures withy a combined damping and feeding. With a new type of planner cross-guide coupler the structure could be made simpler Jeff Neilson

0025 cm Variation u, v, d, and rc Rc 10.

32 Improved 12.5 db Coupler Coupling Histogram for 12.5 db Design Tolerance = +/ cm Variation u, v, d, and rc Rc 10.6mm Frequency of Occurr rence P 15 MW Emax 17 MV/m Hmax 50 ka/m Difference from Design Value (%) Page 32 Jeff Neilson

with minimum enhancement of magnetic surface field relative to closed cavity Cavity

33 Cavity Design Parameters Width and length of coupler arm Iris radius of curvature Cavity radius of curvature Cavity parameters optimized to maximize shunt impedance with minimum enhancement of magnetic surface field relative to closed cavity Cavity radius Beam tunnel radius and thickness Circumference radiusing (Rc) Page 33 Jeff Neilson

5 Max. Mag. Field [KA/m] 342 Max. Electric Field [MV/m] 253 Normalized Max. Mag. Field [290 KA/m] 0.

34 Design Cavity Results for 100 MV/m Parameter 90 Degree Wedge of Cavity Beam Tunnel radius (mm) 2.75 Iris thickness (mm) 2 Stored Energy [J] Q-value 8580 Shunt Impedance [MOhm/m] Max. Mag. Field [KA/m] 342 Max. Electric Field [MV/m] 253 Normalized Max. Mag. Field [290 KA/m] Emax/Accel gradient 2.53 Magnetic Field Hmax Zo/Accel gradient 1.29 Page 34 Jeff Neilson

35 Initial Test Configuration F GHz Ql 5340 β 0.7 P 6.5 MW for 100MV/m acceleration gradient (center cavity) On Axis Field Jeff Neilson

36 Cavity Driven Through RF Feed (F = GHz) 2 3 On Axis Field +5 0 Phase Error (degrees relative to shift) Frequency Response (db) Jeff Neilson

37 Phase Arm Error on Last Cavity Feed (30 Deg) On Axis Field +5 Phase Error (degrees relative to shift) Frequency Response (db) no phase error -40

38 Fabrication Page 38

39 RF Feed Using Biplanar Coupler ~ 10 cm ~ 3 cm ~ 24 cm Page 39

40 Planar Geometry 180 Degree Elbow Return Loss Return Loss Electric Field Frequency (GHz) Page MW Input Power Emax 23MV/m Hmax 73kA/m Jeff Neilson

41 Current Mechanical Design ~25 cm 2.7 kg

43 Bead-pull Frequency (GHz) Pi Mode Zero Mode Q zero Q loaded Q ext Beta On-axis fields Pi-Mode Jim Lewandowski, 7 October 2010

44 Comparison with on-axis coupled structure Breakd down Probability [1/pulse/meter] Breakdown Probability [1/pulse/meter] aêl=0.143, t=2.6mm, Cu aêl=0.143, t=2.6mm, 2WR90-Ò Gradient [MV/m] Gradient [MV/m] aêl=0.143, t=2.6mm, Cu aêl=0.143, t=2.6mm, 2WR90-Ò2 Breakdown Probability [1/pulse/meter] Breakdown Probability [1/pulse/meter] ns shaped pulse ns shaped pulse aêl=0.143, t=2.6mm, Cu aêl=0.143, t=2.6mm, 2WR90-Ò Peak Pulse Heating [deg. C] Peak Pulse Heating [deg. C] aêl=0.143, t=2.6mm, Cu aêl=0.143, t=2.6mm, 2WR90-Ò2

45 Autopsy Coupler cell End cell L. Laurent

46 Less damage in coupler cell Coupler cell End cell L. Laurent

47 Length, Total Peak Power and average gradient of 11 GHz and 3 GHz for a 250 MeV proton linac for compact Therapy Machines Post-injector Accelerator Length [m] GHz GHz Post-injector total peak power [MW] Post-injector Accelerator Length [m] Post-injector total peak power [MW] Power/m [MW/m] Post-injector length and total peak power Power/m [MW/m] Average Gradient [MV/m] GHz 25 MeV 40 MeV 55 MeV 70 MeV Power/m [MW/m] Average Gradient [MV/m] GHz 25 MeV 40 MeV 55 MeV 70 MeV Power/m [MW/m] Average gradient of the post-injector accelerator V.A. Dolgashev, 17:51, 6 April 2009

NLCTA Layout 3 x RF stations 2 x pulse compressors (240ns -300MW max), driven each by 2 x 50MW X-band klystrons 1 x pulse compressors (400ns 300MW /200ns 500MW variable), driven by 2 x 50MW X-band

48 NLCTA Layout 3 x RF stations 2 x pulse compressors (240ns -300MW max), driven each by 2 x 50MW X-band klystrons 1 x pulse compressors (400ns 300MW /200ns 500MW variable), driven by 2 x 50MW X-band klystrons. 1 x Injector: 65MeV, ~0.3 nc / bunch * In the accelerator housing: 2 x 2.5m slots for structures * Shielding Enclosure: suitable up to 1 GeV * For operation: Can run 24/7 using automated controls (Gain = 3.1) AAPM Page 48 S. Tantawi

49 Conceptual X-band Proton Therapy Accelerator 70 MeV Cyclotron 130 MeV X-band standing wave linac Pulse compressor 50 MeV X-band standing wave structure to accelerate and decelerate the p+ beam.

50 Proton Accelerator X-band Beam Energy Trim Goal: Accelerate the proton beam up to 200 MeV with an X-band linac and then Trim the energy by -50 to +50 MeV with a short X-band linac on a moving gantry. To demonstrate the Energy trimming portion, we start from an existing S-band design of a proton therapy linac*, and decelerate the proton beam from 200 MeV to 150MeV, or accelerate it from 200 MeV to 250 MeV with a single X-band Accelerating structure. Proton Beam Input Conditions:* I = 33 µa E = 200 MeV E σ= 0.2 MeV E(n, rms) = 0.25 mm-mrad X-band Trim Accelerator Parameters F = GHz E = 90 MV/m (80% of max limit**) L = 86.2 cm (116 cells) π mode Presented are preliminary.proof of Principle results to demonstrate that it is possible to use an approximately 1 m X-band standing wave accelerator structure to decelerate and accelerate the beam by 50 MeVfrom 200 MeV. More work is needed to optimize The structure and the beam quality. * U. Amaldi et. al, Nuclear Instruments and Methotds in Physics Research A 521 (2004) ** V. Dolgashev, SLAC internal note (2009) A. D. Yeremian, SLAC, 10/25/2010

51 Proton Accelerator X-band Beam Energy Trim Accelerating from 200 to 250 MeV Electric Field in the Structure to Accelerate from 200 to 250 MeV Phase Amplitude 700 Amplitude in (MV/m) Phase in (deg.), Rock the beam phase head and behind the crest to assure the energy spread is correlated so that it can be minimized at the end. (90 MV/m) cell Number A. D. Yeremian, SLAC, 10/25/2010

52 Proton Accelerator X-band Beam Energy Trim Decelerating from 200 to 150 MeV Electric Field in the Structure to Decceleratefrom 200 to 150 MeV Phase Amplitude (90 MV/m) litude in (MV/m) Phase in (deg.), Ampl Rock the beam phase head and behind the RF trough to assure the energy spread is correlated so that it can be minimized at the end cell Number A. D. Yeremian, SLAC, 10/25/2010

53 Very Preliminary Course simulation of the X-band Accelerator for Trimming the Beam Energy from 150 MeV to 250MeV. Accelerating Portions from 200 to 250 MeV Beam Parameters at 250 MeV Energy spread (kev) ial profile (cm) Radi E = 250 MeV E σ= 0.44 MeV R σ = 0.23 mm εrms = 23mm-mrad These are preliminary. proof of principle results to demonstrate that it is possible to use an approximately 1 m X-band standing wave accelerator structure to decelerate and accelerate the beam by 50 MeVfrom 200 MeV. More work is needed to optimize The structure and the beam quality. Bunch length (deg X-band) A. D. Yeremian 10/25/2010

54 Very Preliminary Course simulation of the X-band Accelerator for Trimming the Beam Energy from 150 MeV to 250MeV. Decelerating Portions from 200 to 150 MeV Beam Parameters at 150 MeV Energy spread (kev) ial profile (cm) Radi E = 150 MeV E σ= 0.78 MeV R σ = 0.5 mm εrms = 39mm-mrad These are preliminary. proof of principle results to demonstrate that it is possible to use an approximately 1 m X-band standing wave accelerator structure to decelerate and accelerate the beam by 50 MeVfrom 200 MeV. More work is needed to optimize The structure and the beam quality. Bunch length (deg X-band) A. D. Yeremian 10/25/2010

55 Summary SLAC is leading the experimental work for the developments of high-gradient accelerator structures. unique capabilities for designing, and fabricating RF accelerator structures Unique expertise on ultra-high-power microwave technology Unique facilities Very strong theoretical and modeling groups. The work being done is characterized by a strong national and international collaboration. This is the only way to gather the necessary resources to do this work. The experimental program to date has paved the ground work for the theoretical developments. With the understanding of geometrical effects, we have demonstrated standing and traveling wave accelerator structures that work above 100 MV/m loaded gradient. Standing wave structures have shown the potential for gradients of 150 MV/m or higher Further understanding of materials properties may allow even greater improvements We believe that the elements of technologies needed to build a compact proton accelerator, say 4 meter in length with an energy of 250 MeV is at hand. Acclerator structures RF sources Flexible RF feed for gantry mounted structures Injector system This technology could also be applied in the future for carbon machine. Page 55

Status of High Gradient Tests of Normal Conducting Single-Cell Structures

Status of High Gradient Tests of Normal Conducting Single-Cell Structures Valery Dolgashev, Sami Tantawi (SLAC) Yasuo Higashi (KEK) Robert Siemann Symposium and ICFA Mini-Workshop, July 7th - 10th, 2009