Working Group Summaries: Accelerator RF Technology and Structures Systems and Instrumentation

Working Group Summaries: Accelerator • RF Technology and Structures • Systems and Instrumentation Matthias Liepe Cornell University

RF Technology and Structures We are almost there, But still a lot can and needs to be done.

Accelerator Working Group: RF Technology and Structures Monday, July 14, 8:30-10:30 a.m. 8:30-8:55 Warm and Cold RF Structures Hasan Padamsee 8:55-9:15 Technology Development Program for a Oleg Nezhevenko / Future 34-GHz Linac Vyacheslav Yakovlev 9:15-9:30 Acoustic Localization of RF Structure Breakdowns George Gollin 9:30-9:45 Optimized Cavity Shape for TESLA Valery Shemelin 9:45-10:00 1500 MHz Nb Cavity made of Electro- polished Half-Cells Rongli Geng 10:00-10:15 DC Breakdown Studies Greg Werner 10:15-10:30 Control of Beam Loss in High-Repetition Rate High-Power PPM Klystrons Mark Hess

Accelerator Working Group: RF Technology and Structures Monday, July 14, 8:30-10:30 a.m. 8:30-8:55 Warm and Cold RF Structures Hasan Padamsee 8:55-9:15 Technology Development Program for a Oleg Nezhevenko Future 34-GHz Linac 9:15-9:30 Acoustic Localization of RF Structure Breakdowns George Gollin 9:30-9:45 Optimized Cavity Shape for TESLA Valery Shemelin 9:45-10:00 1500 MHz Nb Cavity made of Electro- polished Half-Cells Rongli Geng 10:00-10:15 DC Breakdown Studies Greg Werner 10:15-10:30 Control of Beam Loss in High-Repetition Rate High-Power PPM Klystrons Mark Hess

Strategy: start with 23.5 MV/m Structures tested to 35 MV/m before installation Copper Niobium 1.3 GHz 1 m 11.4 GHz Start with Ea-loaded=50 MV/m (65MV/m-unloaded) Fewer structures 20,600 L = 21 km 18,500 L = 11.1 km Why 11.4 GHz? Peak RF Power needed to reach gradient a 1/√ frequency RF Losses = 55 W ea. Run pulsed at a duty factor of 0.7% Need RF peak power = 1.2x109 watt Dynamic heat load at 2 K = 10 kW + Static + safety = 30 kW refrigerator.. AC power = 22 MW RF Losses = 80 MW/m ! Total peak RF power = 1012 watt Duty Factor = 0.006% AC Power = 150 MW

The best !

37 MV/m in Fully Equppied Cavity i.e. high power test and 1/8th of a TTF Linac module

Technology Development Program for a Future 34-GHz Linac • Oleg Nezhevenko • Goal: extend present 11 GHz RF technology by a factor of 3 to 34 GHz with hope to increase achievable gradients. • Built a 34 GHz magnicon (10 MW, 0.5 s) and cavity for pulsed heating tests. • Designed a 34 GHz 19 cell accelerating cavity.

The hard limit for the increase in accelerating gradient in s.c. cavities is the surface magnetic field. Optimize cavity shape: One can, for example, sacrifice 20 % of electric field to gain 10 % in magnetic field and so increase the Acc. Rate by 10 %. old new

Motivation: Do heat treatment and electropolishing on half cells to reduce cost in s.c. cavity production.

DC breakdown studies on copper and niobium surfaces. • found starbursts and craters after breakdowns • found Manganese on all heat treated copper samples 50 um 145MV/m

Theoretical studies: Why do some klystrons show beam loss (and some don’t)? y x z L L Vz a r a r Vz Diagrams of Bunched Beam Models Pencil Beam Model (Presented at Arlington Meeting) Finite Size Beam Model (New)

Comparison of Bunched Beam Models to Experiment gbsz/a=0.71 gbsz/a=0.36 gbsz/a=0.0 Red Curve: Pencil Beam Blue Curves: rb/a=0.5

Systems and Instrumentation Good controls and instrumentation are essential for LC. Much work in progress, but a lot more needs to be done.

Accelerator Working Group: Systems and Instrumentation Monday, July 14, 10:55-12:55 10:55-11:15 Accelerator Instrumentation RD Marc Ross 11:15-11:35 Prototype Synchrotron Radiation Telescope Jim Alexander 11:35-11:55 Design and Fabrication of a Radiation-Hard 500 MHz digitizer K K Gan 11:55-12:15 Nanometer resolution Beam Position Monitors Marc Ross 12:15-12:35 Nanometer BPM supports and movers Jeff Gronberg Tuesday, July 15, 1:50-3:50 p.m. 1:50-2:10 TTF data acquisition Tim Wilksen 2:10-2:30 Beam size diagnostics using diffraction radiation Bibo Feng 2:30-2:50 A0 coherent radiation diagnostics Court Bohn

Overview of beam instrumentations and controls; importance and influence on cost, performance and reliability of LC. • Examples: • correlation monitors • Multibunch behavior of u-wave cavity BPM’s • Long. phase space diagnostics based on deflecting RF • Marc’s Conclusion: • HEP must aggressively attack Controls/Instrumentation issues

Image synchrotron radiation from damping rings •  Snapshot from transverse bunch shape, single bunch resolution • Present: explore parameter space, identify key issues. • Next: system pro-design • Future: Test structures,…

radiation hard (> 60 MRad) • somewhat beyond state-of-the-art • started with design, are funded by DOE for design/simulation in first year • goal: has most circuit blocks ready for prototyping by end of first year

What are the uses of nanometer-resolution BPMs? – Measure beam position with accuracy better than support stability • Use the beam as a mechanical ‘device’ to prove active stabilization? – Measure beam parameters other than position • Many applications in beam manipulation • RF BPM ideal • 3 Balakin BPMs installed at ATF. • Started to study performance.

To demonstrate nanometer resolution the BPMs must be stable at the nanometer level with respect to one another. • Designed 3 hexapod-structure to hold and align BPMs. • Mechanical modes of the structure should be above 200 Hz, where they do not harm. • Vibration simulations are done, alignment frame is under construction. • Beam test at ATF in October 2003.

Cornell, DESY and OSU initiated a joined project to design and develop a TTF 2 data acquisition by using collaboration technologies as an example for a possible future GAN scenario. • Built on top of the DOOCS accelerator control system. • Development of collaborative tools. • First application: TTF2 FEL (2004). 50 to 100 GB/day.

y x e- z q a Why use diffraction radiation for beam diagnostic? • Non-invasive: Diffraction radiation through a slit. • Beam size diagnostics: longitudinal and transverse • Beam position monitor: radiation intensity vs. beam position • More beam information: beam energy and emittance • Status and Plans at Vanderbilt FEL: • Studies of diffraction radiation • Designed and built a interferometer • Future: • Radiator: vacuum chamber and slit actuator • Longitudinal bunch length experiments • Measurement of DR angular distribution • Transverse beam dimension experiments

Coherent radiation studies at A0 for beam diagnostic • Built a new, compact Michelson interferometer • Future goal: single shot measurement (with Fresnel mirror, no moving parts)

Thank you Speakers! This was fun!

Working Group Summaries: Accelerator RF Technology and Structures Systems and Instrumentation