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

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 dbowring@fnal.gov March 5, 2014

Overview Modular Cavity Plan D. Bowring Introduction 1 What’s the big idea? Goals 2 Elements of a high-power run Run Plan 3 Questions we need to address Questions Instrumentation 4 Instrumentation and analysis Who? 5 Who will be involved? Figure : Breakdown damage on the All-Seasons cavity coupler region.

Modular Cavity Plan D. Bowring Introduction Goals Run Plan Program Goals Questions Instrumentation Who?

We want to build an ionization cooling channel. To be specific, we want to build a functioning, efficient vacuum Modular Cavity Plan RF cooling channel. D. Bowring Introduction Goals Run Plan Questions Instrumentation Who? 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?

The modular cavity solves several experimental problems. Modular Cavity Plan Pillbox E-field ASC E-field M.C. E-field D. Bowring Introduction Goals Run Plan Questions Instrumentation Who? Problem M.C. Solution When breakdown is geometry- Highest surface E-fields on dependent, what can we say “beam axis”. about gradients? How can we track and repair Demountable end plates for in- damage in – essentially – a spection, repair, material stud- Faraday cage? ies.

So what do we expect from the M.C. program? Modular Cavity Plan D. Bowring 1 Assess breakdown rates with and without magnetic fields Introduction without field enhancement at the coupler. Goals 2 Investigate the effects of end plate material properties on Run Plan breakdown rate. Questions Cu, machined to < 16 µ -in R a and chemically polished Instrumentation Clean, fully-annealed Cu Who? 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.

We address these issues with a modular design. Modular Cavity Plan D. Bowring Introduction Goals Run Plan Questions Instrumentation Who?

We address these issues with a modular design. Modular Cavity Plan D. Bowring Introduction Goals Run Plan Questions Instrumentation Who?

Modular cavity assembly & layout in Lab G solenoid Modular Cavity Plan D. Bowring Introduction Goals Run Plan Questions Instrumentation Who? NB: This is an outdated drawing.

One more photo Modular Cavity Plan D. Bowring Introduction Goals Run Plan Questions Instrumentation Who?

Modular Cavity Plan D. Bowring Introduction Run Plan Goals Run Plan Questions Three elements to the run plan: Instrumentation 1 Initialization/Inspection Who? 2 Conditioning 3 Run

Initialization Phase Modular Cavity Plan D. Bowring Introduction 1 Inspect Goals 2 Purge with N2, Run Plan Resources Questions install, pump 1 3p × 1d (sci/eng, technicians) Instrumentation 3 Cold test (for 2 4p × 4d (sci/eng, technicians) Who? instrumentation 3 3p × 1d (sci/eng) check, not RF confidence)

We will inspect the cavity surface at every reasonable opportunity. Modular Cavity Plan D. Bowring Introduction Goals Run Plan Questions Instrumentation Who? What will we do with this data? c.f. Katsuya’s talk for example.

Conditioning Phase Modular Cavity Plan Initialization D. Bowring Ramp RF @ 0.4 MV/m/h Pre-run Introduction inspection Goals Vacuum, instrumentation Run Plan Spark rate ≥ 10 − 5 no Pump-down, leak Questions from ≥ 10 sparks? check Instrumentation Cold test Who? yes Safe operating gradient (S.O.G.) established. Cavity Inspection Testing

Testing Phase Modular Cavity Plan Conditioning Re-initialize, ramp to S.O.G. as before. D. Bowring Introduction Further Assessment Reaches Goals no S.O.G.? What conclusions can we Run Plan draw from these failures? Questions yes Conditioned to Instrumentation metastable surface? Then reexamine ramp Who? 3 × 10 6 pulses rate, “3 × 10 6 no @ S.O.G.? pulses”. Inspection changes yes surface? How, if done in clean room? Cavity Inspection Good run. Inspect, prep for next run.

How much time do we need? Modular Other time estimates Estimated time per run Cavity Plan http://mice.iit.edu/mta/temp/MS D. Bowring Ramp gradient at Task Time People 0 . 4 MV/m/h Introduction Inspect 1d 2-3 Goals When a spark occurs, Load in LGS 2d 4 power cuts by half and Run Plan LLRF meas. 2d 3 ramp resumes. Questions Pumpdown 2d 3 Instrumentation Clean room 1d 3 ASC had < 1 spark per Who? day. A single “run” to The Crux establish S.O.G. typically takes 2-3 weeks of How many runs are required to convince round-the-clock running in shifts A ourselves whether d significant effort! dt S.O.G. = 0 ?

Modular Cavity Plan D. Bowring Introduction Goals Run Plan Open Questions Questions Instrumentation Who?

MTA RF Questions Modular Statistics problem relevant to all MTA Cavity Plan cavities: D. Bowring Can we establish a single value of Introduction the operating gradient for a given Goals set of plates with any confidence? Run Plan How do we find equilibrium? (See Questions Instrumentation cartoon at right.) Figure : This is a Who? Does measurement order ( B = 0 vs situation that has B = 3 T) matter? caused some angst for From Mark: How can we establish us in the past. the “lifetime” of a given cavity surface? These questions should be a priority of the data analysis effort.

How is damage related to gradient limits? Modular Cavity Plan D. Bowring Introduction Goals Run Plan Questions Instrumentation Who? 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.

Modular Cavity Plan D. Bowring Introduction Goals Run Plan Questions Instrumentation Instrumentation Who?

Instrumentation Modular Cavity Plan D. Bowring Standard Data Under Development Introduction RF waveform capture These are all potentially very Goals and characterization useful to the M.C. analysis Run Plan effort. How can I help? Spark detection Questions Spectrometry Vacuum quality Instrumentation Microphonic BD Who? Radiation in MTA localization We’re working on Dark current via centralizing and Faraday cup standardizing our run data. Al (and Ben?) we need to talk soon about this.

Modular Cavity Plan D. Bowring Introduction Goals Run Plan Questions Who will be involved? Instrumentation Who?

Who will be involved in this effort? Modular Cavity Plan D. Bowring Introduction Goals Run Plan Questions Instrumentation Who? 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 others. Who else will be involved? I don’t want to email everybody in MAP every time there’s a M.C. meeting.

Thanks for your attention. Modular Cavity Plan D. Bowring Introduction Goals Run Plan Questions Instrumentation Who?