Summary of Proposal RFQ Injection for

High Intensity Neutrino SourcesJanet Conrad

Primary Reviewer

Rick Baartman

FY16 Intermediate Neutrino Research Progam December 7-8,

2015 Germantown, Md

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• Physics Goals/Measurement

Background: The current longer range plan of the team is to accelerate at least 5mA of singly charged molecular hydrogen to an energy of 60MeV/amu. The intention is to do this with a compact cyclotron.

The proposal is to construct an experiment to demonstrate feasibility and a gain in efficiency when an RFQ is used to accelerate and bunch the beam from the ion source into compact cyclotrons, rather than using traditional transport and bunching techiques.

Summary of Proposed Research (1)

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A test stand is to be assembled at MIT. This would use some components from the “Vancouver test” stand, but includes in addition the RFQ and a 1MeV cyclotron.

Budget (profile and totals)• Major Items of Equipment: roughly 225k$ for RFQ,

200k$ for cyclotron, 300k$ for ancillary, total for test stand is 1M$.

• Contract services, computer services and indirect costs: 400k$.

• Personnel Costs: 160k$

Summary of Proposed Research (2)

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The Proposed Test Stand

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List of institutions/collaborators• Janet Conrad, MIT• Jose Alonso, MIT• Joseph Minervini, MIT• William Barletta, MIT

Significant past contributions relevant to the proposal: A previous project built a test stand in collaboration with BEST cyclotrons demonstrated 15mA of H2

+. But this is unbunched.

Summary of Collaboration

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• Scientific and/or Technical Merit of the Project:1,6,3,5,5,4• Appropriateness of the Proposed Method or Approach:

2,6,4,6,5,5• Competency of Personnel and Adequacy of Proposed

Resources: 2,5,6,5,5,4• Reasonableness and Appropriateness of the Proposed

Budget: 4,5,5,4,4,4• Relevance of the proposed research to the goals of the

Intermediate Neutrino Research Program: 6,6,3,5,4,2• Technical feasibility to produce publishable results with five

years after initial funding: 3,6,6,4,5,5• Data Management Plan of the Proposed Research: 3,5,6,5,6,4

• Primary reviewer (me) is the first score.

How well does the proposal meet the Review Criteria

Proposal Summary

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Observations: • Current compact cyclotrons running at the space charge limit

have peak current of about 10mA.• This proposal is for peak current of 100mA (5mA/5% phase

acceptance).• Key point: Space charge limit depends on peak, not average,

current.• What the proposal wants to achieve is an order of magnitude

from what has been demonstrated and further, as shown below, is physically impossible.

Recommendation:• I therefore recommend against supporting it.

Space Charge PhysicsExample envelope calculation

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RFQ beam injected into InflectorGrows to 60mm in lengthShould be 4mm.

i.e., this black curveShould be below 0.2cmOn this graph.

Even if directly injected RFQ to Inflector

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2cm half-length

Even if re-Bunched:

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December 7-8, 2015 Germantown, MD Intermediate Neutrino Research Program

Black curve should be in this blue box

Bunch radius typically 1cm:5 times bigger than we want.

Simple calculation: Debunching Sphere

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Space Charge LimitSo optics must have a scaling focal length that is SMALL compared with 5cm. RFQ easily achieves this. But cyclotron is 15cm.

With this length scale, and the small phase acceptance (compared with H- cyclotrons), I estimate space charge limit as ~0.2mA.

And in this case RFQ hinders rather than helps.

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Excerpts from Reviewer Comments

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December 7-8, 2015 Germantown, MD Intermediate Neutrino Research Program

Negative: Akira Konaka: “For a neutrino experiment using this technology, a much larger investment and longer period are required than what is considered in the Intermediate Neutrino Research Program.”

All other comments, but mine, uniformly positive.

Positive: Jerome Busenitz: "The proposed work, if successful, would significantly impact both Accelerator… and neutrino physics”

This is true but.

Not one of the secondary reviewers has expertise in compact cyclotrons., so would not be aware that the proposal is an order of magnitude beyond the space charge limit that has been achieved.

Summary and General Comments

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December 7-8, 2015 Germantown, MD Intermediate Neutrino Research Program

• The goal of achieving 5mA average current circulating inside the phase acceptance of a separated turn cyclotron is not realistically achievable.

• The proposed RFQ can achieve 5mA, 80keV at 33MHz but this is of no use to the neutrino program.