The Experimental Plan for the Introduction 805 MHz Modular Cavity - - PowerPoint PPT Presentation

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The Experimental Plan for the Introduction 805 MHz Modular Cavity - - PowerPoint PPT Presentation

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Modular Cavity Plan D. Bowring The Experimental Plan for the Introduction 805 MHz Modular Cavity Goals RF Breakdown Meeting Run Plan Questions Instrumentation Daniel Bowring Who? Fermi National Accelerator Laboratory Batavia, IL

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Modular Cavity Plan

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Introduction Goals Run Plan Questions Instrumentation Who?

The Experimental Plan for the 805 MHz Modular Cavity

RF Breakdown Meeting Daniel Bowring

Fermi National Accelerator Laboratory Batavia, IL dbowring@fnal.gov

March 5, 2014

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Modular Cavity Plan

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Introduction Goals Run Plan Questions Instrumentation Who?

Overview

1 What’s the big idea? 2 Elements of a high-power run 3 Questions we need to address 4 Instrumentation and analysis 5 Who will be involved?

Figure : Breakdown damage on the All-Seasons cavity coupler region.

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Modular Cavity Plan

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Introduction Goals Run Plan Questions Instrumentation Who?

Program Goals

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Modular Cavity Plan

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Introduction Goals Run Plan Questions Instrumentation Who?

We want to build an ionization cooling channel.

To be specific, we want to build a functioning, efficient vacuum RF cooling channel. The physics of RF breakdown is a fascinating problem that has been unsolved for > 100 years. The solution of this problem should not be a precondition for building a muon accelerator. How solved does this problem need to be in order for us to build a machine?

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Modular Cavity Plan

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Introduction Goals Run Plan Questions Instrumentation Who?

The modular cavity solves several experimental problems.

Pillbox E-field ASC E-field M.C. E-field

Problem M.C. Solution When breakdown is geometry- dependent, what can we say about gradients? Highest surface E-fields

  • n

“beam axis”. How can we track and repair damage in – essentially – a Faraday cage? Demountable end plates for in- spection, repair, material stud- ies.

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Modular Cavity Plan

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Introduction Goals Run Plan Questions Instrumentation Who?

So what do we expect from the M.C. program?

1 Assess breakdown rates with and without magnetic fields

without field enhancement at the coupler.

2 Investigate the effects of end plate material properties on

breakdown rate.

Cu, machined to < 16 µ-in Ra and chemically polished Clean, fully-annealed Cu Beryllium Other materials? It would be useful to try W, Mo, Cu-Au, Cu-Zr.

3 Inspect the cavity frequently and reliably enough to make

concrete statements about the difference between damage with and without B-field.

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Modular Cavity Plan

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We address these issues with a modular design.

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Modular Cavity Plan

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Introduction Goals Run Plan Questions Instrumentation Who?

We address these issues with a modular design.

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Modular Cavity Plan

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Introduction Goals Run Plan Questions Instrumentation Who?

Modular cavity assembly & layout in Lab G solenoid

NB: This is an outdated drawing.

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Modular Cavity Plan

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One more photo

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Modular Cavity Plan

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Introduction Goals Run Plan Questions Instrumentation Who?

Run Plan

Three elements to the run plan:

1 Initialization/Inspection 2 Conditioning 3 Run

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Modular Cavity Plan

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Introduction Goals Run Plan Questions Instrumentation Who?

Initialization Phase

1 Inspect 2 Purge with N2,

install, pump

3 Cold test (for

instrumentation check, not RF confidence) Resources

1 3p × 1d (sci/eng, technicians) 2 4p × 4d (sci/eng, technicians) 3 3p × 1d (sci/eng)

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Introduction Goals Run Plan Questions Instrumentation Who?

We will inspect the cavity surface at every reasonable opportunity.

What will we do with this data? c.f. Katsuya’s talk for example.

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Modular Cavity Plan

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Introduction Goals Run Plan Questions Instrumentation Who?

Conditioning Phase

Initialization Pre-run inspection Vacuum, instrumentation Pump-down, leak check Cold test Ramp RF @ 0.4 MV/m/h Spark rate ≥ 10−5 from ≥10 sparks? Safe operating gradient (S.O.G.) established. Cavity Inspection Testing yes no

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Modular Cavity Plan

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Introduction Goals Run Plan Questions Instrumentation Who?

Testing Phase

Conditioning Re-initialize, ramp to S.O.G. as before. Reaches S.O.G.? Further Assessment What conclusions can we draw from these failures? Conditioned to metastable surface? Then reexamine ramp rate, “3 × 106 pulses”. Inspection changes surface? How, if done in clean room? 3 × 106 pulses @ S.O.G.? Cavity Inspection Good run. Inspect, prep for next run. yes yes no no

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Modular Cavity Plan

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Introduction Goals Run Plan Questions Instrumentation Who?

How much time do we need?

Estimated time per run Ramp gradient at 0.4 MV/m/h When a spark occurs, power cuts by half and ramp resumes. ASC had < 1 spark per day. A single “run” to establish S.O.G. typically takes 2-3 weeks of round-the-clock running in shifts A significant effort! Other time estimates

http://mice.iit.edu/mta/temp/MS

Task Time People Inspect 1d 2-3 Load in LGS 2d 4 LLRF meas. 2d 3 Pumpdown 2d 3 Clean room 1d 3

The Crux How many runs are required to convince

  • urselves whether

d dt S.O.G.= 0?

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Open Questions

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Modular Cavity Plan

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MTA RF Questions

Statistics problem relevant to all MTA cavities: Can we establish a single value of the operating gradient for a given set of plates with any confidence? How do we find equilibrium? (See cartoon at right.) Does measurement order (B = 0 vs B = 3 T) matter? From Mark: How can we establish the “lifetime” of a given cavity surface?

Figure : This is a situation that has caused some angst for us in the past.

These questions should be a priority of the data analysis effort.

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Modular Cavity Plan

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Introduction Goals Run Plan Questions Instrumentation Who?

How is damage related to gradient limits?

From W. Wuensch, High-gradient Workshop, Argonne 2003. Damage is relative. Plenty of anecdotes about damaged cavities that still perform as designed. We can try to quantify the effect of damage on gradient.

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Modular Cavity Plan

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Instrumentation

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Modular Cavity Plan

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Introduction Goals Run Plan Questions Instrumentation Who?

Instrumentation

Standard Data RF waveform capture and characterization Spark detection Vacuum quality Radiation in MTA We’re working on centralizing and standardizing our run data. Al (and Ben?) we need to talk soon about this. Under Development These are all potentially very useful to the M.C. analysis

  • effort. How can I help?

Spectrometry Microphonic BD localization Dark current via Faraday cup

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Modular Cavity Plan

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Who will be involved?

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Modular Cavity Plan

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Introduction Goals Run Plan Questions Instrumentation Who?

Who will be involved in this effort?

Some of you have already expressed interest in this or that aspect of the modular cavity effort. Some of you have already been volunteered by myself or

  • thers.

Who else will be involved? I don’t want to email everybody in MAP every time there’s a M.C. meeting.

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Thanks for your attention.