WG8 – Linac Front-End Bob Webber/Derun Li Group Leaders Project X Collaboration Meeting September 8-9, 2010

WG Session #1 Session 1 – Front-End Group met jointly with: –Linac Integration Group –Pulsed Linac & Injection Group –Instrumentation Group –Talks CW Linac Design - Nikolay Solyak (Fermilab) SNS Diagnostics - John Galambos (Fermilab) RFQ, LEBT and MEBT Issues - John Staples (LBNL) Project X Collaboration Meeting Sept 8-9, WG8 Summary Page 2

H - -source: 10 mA CW RFQ (RT): 325 MHz (possible MHz), ~ 2.5 MeV, 1/10mA avg/peak MEBT (room temperature): Chopper RT bunching cavities, P < 5kW each Triplet (RT) optics (keep round beam) Low-energy SC 325 MHZ linac ( MeV) 3 families of single-spoke cavities Solenoidal focusing (SC), doublet or triplet is also possible Separate cryomodules with warm inter-connection Two families of 650 MHz cavities to cover 160 MeV -2 GeV range Low- β (LB) β =0.61 and high- β (HB): β =0.9 cavities Focusing: Doublet s, ILC cavities in the high-energy section (2 GeV-3 GeV) Type-4 Cryomodules, FODO focusing; Cryo-segmentation  cryo-string Local power distribution: One CW RF sources per cavity Solid state amplifier at 325MHz and 650 MHz (?) IOT or solid state for 650 MHz and 1300 MHz SC CW 3GeV Linac: conceptual design 3 Project X Collaboration Meeting Sept 8-9, WG8 Summary

4Managed by UT-Battelle for the U.S. Department of Energy Presentation_name Beam Loss Monitors One of the most important diagnostic tools in a high power facility Sensitive: can easily detect loss of a MW beam View of loss monitors across the SNS facility BLM / Radiation Detection Also Valuable Tool for SC Cavity Diagnostic

5Managed by UT-Battelle for the U.S. Department of Energy Presentation_name Other Diagnostic Thoughts (User perspective) For commissioning you need the most simple of diagnostics to work in the most simple fashion For reducing halo beam loss you need sophisticated measurements of beam tails – this is what experts want to work on Diagnostics tend to be the 1 st item cut, when cost issues arise Integration of information from different diagnostics is important – Triggered data acquisition from the same time – Interface with end user and high level software Must be usable by non-experts quickly, repeatable, …

6Managed by UT-Battelle for the U.S. Department of Energy Presentation_name

7Managed by UT-Battelle for the U.S. Department of Energy Presentation_name

WG Session #2 Session 2 – Front-End Group met jointly with: –Instrumentation Group –Talks Indian RFQ Development - Sunny Rao (BARC) HINS Beam Optics Topics - Eliana Gianfelice-Wendt (Fermilab) New Front End FNAL Linac - Cheng-Yang Tan (Fermilab) Other Chopper Ideas - Greg Saewert (Fermilab) MOSFET Chopper - Tao Tang (SLAC) PX Instrumentation R&D at HINS - Vic Scarpine (Fermilab) Project X Collaboration Meeting Sept 8-9, WG8 Summary Page 8

We have total 6 RFQ programs in India RFQ Vane Type  MHz,3 MeV and 30 mA proton  350 MHz, 400 keV and 1 mA deuteron  MHz, 3 MeV and 25 mA H- pulsed Rod Type  37 MHz, A/q ≤ 14 at VECC  75 MHz, A/q≤ 7 at TIFR-BARC  48.5 MHz, A/q≤ 6 at IUAC. Vane Type Prototypes

Project X Collaboration Meeting Sept 8- 9, WG8 Summary 10

Project X Collaboration Meeting Sept 8- 9, WG8 Summary 11

9/8/2010Project X Collaboration Meeting12 Helical microstrip line prototype Microstrip Z O = 175 ohms Microstrip helix:.10” (ave.) conductor width.23” (ave.) pitch 8.25” long (10.5 ns electrical length, 35-1/2 turns) 1.0” OD, 1/8” dielectric over.75” ID ground Voltage pickup, 1 cm x 3 cm, 0.85 cm from conductor strip Microstrip line dielectric spiral cut from a 1” OD,.75” ID polycarbonate tube and slid over cylindrical ground. Conductor is copper tape attached to dielectric OD. Input Output

13 Proof of Principle Experiments: Output of the HSMs and Adder Switching time ~1.4 ns Output voltage ~3.3kV Adder with 4 HSMs Single HSM Turn on time ~1.5 ns Output voltage ~920V

WG Session #3 Session 3 – Front-End Group met separately: –Talks H- Ion Source for Project X - Qing Ji (LBNL) H- Sources and LEBTs for 1 MW Beams - Martin Stockli (SNS) H- ion source activities at FNAL - Dan Bollinger (Fermilab) LBNL PX Proposal - Derun Li (LBNL) Project X Collaboration Meeting Sept 8-9, WG8 Summary Page 15

Project X Collaboration Meeting Sept 8- 9, WG8 Summary Page 16

17Managed by UT-Battelle for the U.S. Department of Energy Presentation_name Source replacements can be as short as 5 hours (~1 hour replacing the source, 3 hours conditioning and cesiation, and ~1 hour for beam tuning). Over the past 2 years we have ramped up the ion source service cycle from 2 to 3, to 4, and to 5 weeks without encountering old-age problems or failures. After an initial cesiation with ~3mg of Cs, the beam persists for up to 1 month without an apparent decay. We attribute this fact to a persistent Cs mono layer. We are in the process of characterizing our source to understand why we are able to produce such high beam currents without sputtering away the Cs layer. Since recently we are producing beam currents that are too high for operations. We continue to gain significant insights into the operation of H- RF sources, which helps us solve operational problems, extend the useful life of the sources, and improve the consistency of their performance. The Successes with the SNS Ion Source & LEBT

18Managed by UT-Battelle for the U.S. Department of Energy Presentation_name  Symmetry minimizes tuning: Reverse the dipole and fine tune! We expect the SNS electrostatic LEBT to work up to 3 MW, but the heating of the passively cooled lenses is a significant risk. Accordingly, we are assembling a prototype 2-solenoid LEBT as an alternative. However, the ultimate availability appears to be a 2-source LEBT: when one source fails, Operations switches sources in less than 1 hour.  Both ion source beam lines allow for replacing, testing, and conditioning the source while the other is in production. A SNS 2-source LEBT designed for 3 MW RFQ Dipole chopper Sole- noids solenoid 2 ion sources The 2 source LEBT will evolve from our 2-solenoid LEBT by inserting a Y-magnet between the solenoids!  Such source switching magnets are common, but they are normally not built to stringent requirements. A prototype is needed to proof that the low emittance beam can be bent with minimal emittance growth!

HINS H- direct magnetron HINS source is a round aperture based on a BNL design J. Alessi 4/10/02 The source has a spherical dimple and round anode aperture. The dimple helps to focus the plasma near the anode opening allowing for greater extraction efficiency

Ion Sources Filament driven H - source provides a rapid-entry, low risk solution, but with marginal emittance; need more R&D: Filament driven H - source provides a rapid-entry, low risk solution, but with marginal emittance; need more R&D: – Improve lifetime and optimize extraction system – Expedite the R&D of LEBT We propose an R&D effort on a next generation, CW/pulse operation, RF H - ion source with external antenna We propose an R&D effort on a next generation, CW/pulse operation, RF H - ion source with external antenna – Advanced RF-driven H- ion source Longer lifetime (> 500 hr) Longer lifetime (> 500 hr) Better emittance Better emittance Flexible pulsing structure Flexible pulsing structure – LBNL is experienced in RF sources research and operation at MHz for both proton and H - production. 20 Proposal for the Front-End System of PX, D. Li, LBNL, 9/8/2010

LEBT R&D with Ion Source The ion source + LEBT will be developed and tested incrementally The ion source + LEBT will be developed and tested incrementally – Extraction and 30 keV acceleration from the ion source – Electron diversion and trapping – Ion source emittance measurements – Pulsed switching magnet then added – Emittance, neutralization time measurements – Matching section into RFQ that accommodates two ion sources operating at different current levels – 4-phase chopper implementation at RFQ entrance – Establish matching parameters required by RFQ The LEBT will be fully configured and tested during R&D phase The LEBT will be fully configured and tested during R&D phase 21 Proposal for the Front-End System of PX, D. Li, LBNL, 9/8/2010

RFQ Accelerator Conceptual preliminary designs of CW RFQ accelerators at two RF frequencies: MHz and 325 MHz (preferred) Conceptual preliminary designs of CW RFQ accelerators at two RF frequencies: MHz and 325 MHz (preferred) R&D on 325 MHz CW RFQ R&D on 325 MHz CW RFQ Beam dynamics (kick-bunch design) Beam dynamics (kick-bunch design) RF structure design RF structure design Structure ends (cut-backs) Structure ends (cut-backs) Mode separations (pi-mode rods) Mode separations (pi-mode rods) RF couplers RF couplers Tuners and probes Tuners and probes Engineering designs of NC CW RFQ structures Engineering designs of NC CW RFQ structures Mechanical design Mechanical design Thermal management Thermal management Prototypes of key fabrication techniques Prototypes of key fabrication techniques 22 Proposal for the Front-End System of PX, D. Li, LBNL, 9/8/2010

MEBT and MEBT Choppers – In collaboration with Fermilab in MEBT and choppers studies – FNAL has developed a MEBT lattice structure We will use it We will use it – LBNL would implement the FNAL beam dynamics design with wide-band deflectors designed by FNAL – Or as a backup solution, narrow-band deflectors designed by LBNL 23 Proposal for the Front-End System of PX, D. Li, LBNL, 9/8/2010

WG8 Summary Diverse group of good presentations on relevant topics and activities A few selected points –The LEBT is where the front-end beam physics lies –There seems to be a movement away from electrostatic LEBTs –We need to clarify w/LBNL specific responsibilities for MEBT (fast chopper vs. narrowband chopper environment) –Pre-chopper should be de-coupled from ion source accelerating/focusing electrodes –“most H - is ‘surface-produced’”; there is a real need for understanding of Cesium control --- scientific opportunity here Many excellent ideas and plans for R&D efforts Limited resources will force difficult and important prioritization decisions LBNL/SNS/Fermilab H - ion source collaboration is well positioned to take the necessary steps toward a Project X ion source if properly supported Chopper remains the most difficult challenge Project X Collaboration Meeting Sept 8-9, WG8 Summary Page 24

Points from other WG Summaries Things to remember from close-out –Galambos (WG7) talked of need for scrapers in MEBT & throughout linac for linac beamloss control; SNS has no space for such in warm section; scraped beam has ‘continuous’ time structure; cleaning chopper edges helps ring losses, but not linac losses – no comment on power absorbed by their MEBT scrapper –SNS will try proton study in Dec 10 to assess intrabeam H- loss theory WG2 (cavities and cryomodules) Suggest splitting SSR0 cyrostat Project X Collaboration Meeting Sept 8-9, WG8 Summary Page 25