Proton Driver Meeting

29 - March - 2001
FNAL Committium

Presentations:-

• Mayda Velasco: Introduction
• Weiren Chou: Introduction to the Brighter Booster Project
• Chuck Ankenbrandt: Brighter Booster - Old and New
• Milorad Popovic: Linac in the Booster Tunnel
• P Spentzouris: Low Energy Neutrino Option

1. Presentations on the machine
2. Presentations on the physics case
3. Questions and answers about the machine and how it relates to the proposed physics programs

The study report from last year is now available in hardcopy: Fermilab-TM-2136.

The director's letter indicates that the proton driver is a backup project. The planned course of the lab is: Run II, BTeV, NLC. The proton driver upgrade (PDU) will be considered if there is a major change, and if its cost can be reduced by about a factor of two.

As a consequence of the director's letter, our goal now is to reduce the total cost by a factor of two.

This machine will be discussed at SNOWMASS, in machine session M6, and in experimental sessions E1 (muon collider) and E5 (fixed target).

Some parts of the base design will be implemented, as they will directly benefit the current programs. Not yet committed: the Linac improvements.

There are several variations to the base line proposal to upgrade the Linac. Most of these involve essentially no downtime for the TeVatron or Main Injector. See Appendix A of the report.

We will try to get high power (such as 2 MW) at a reduced proton energy (such as 8 GeV). We will consider a small-scale project, such as an upgrade to the Linac front-end and energy, those this may entail some downtime. Note there is a 3-month shutdown in 2003 to replace the Si detectors of D0 and CDF. This would be a good time to make connections.

What is the funding limit before the upgrade becomes impossible for Run II?

We have only until May to write a proposal. The machine section should be limited to 15 pages (though it can refer extensively to the 2000 design report). Main item for this deadline: the run. We need to get the lattice down to achieve the cost goal.

Charge: What physics will this device bring?

1. If we iterate on the extensive work already done, we can get a major improvement for the proton driver at half the cost.
2. An aggressive Linac upgrade will help Run II a lot.
3. IF we transmit these messages forcefully, then we might actually get to do this project.

Question: What will the cost be?
Answer: Ring = $100M. Linac energy upgrade by 200 MeV: $20M. Some of these overlap, so the total is no more than $120M.

History:

• 90's: muon collider idea introduced: requires a much better p source
• 1997: summer study proposes a 2-ring approach. stage the project
• 2000: "Proton Driver Design Report" proposes a single-ring replacement for the Fermilab Booster. recognizes that 8 GeV is better than 16 GeV.
• 2001: response of the Directorate: great work, but this proposal is too expensive and too late for Run II.

A real improvement requires a Linac upgrade. (See App B of the DR.)

We will base costing on simple scaling rules.

Result: E = 8 GeV, Booster circum (474 m), 40pi, $100M (cf $244M). The savings wrt $122M allows for a substantial upgrade to the Linac energy: 600 MeV.

The design report has a number of nice ideas, some of which may well apply to the existing `old' booster. Also, we know we can double the number of protons from the Linac, which is source limited.

Fermilab-Conf-98/266 : first proposal of this idea
Fermilab-Pub-96/046 : What the Linac can do.

The technology of the present Linac dates from 1993, so an upgrade based on the same technology entails little risk. The only risky part is the presence of curves sections. But this is not believed to be a serious challenge.

The cost is $1.5M/20 MeV, and there would be almost no civil construction.

It could be completed in under two years from now, thanks to spare parts and Cu already on site.

Big concern: how to stage and schedule this work? We would need a shutdown of at most 2 months.

There is space in the tunnel and the galley above.

Question: Can all this be done in time to benefit Run II?
Answer: yes, there is no new technology.

Question: Do you really need no R&D given that the Linac must be bent? [There was a long discussion, with some concerns expressed and some controversy regarding the difficulties the bent sections would pose.] The dispersion can be accommodated.

Comment: This is an extension of an existing style of Linac. The number of protons could be increased from 5 to 9x10**13 in two years' time. There could also be an energy upgrade by 200 MeV. Electron cooling, however, would take longer.

Motivation.

Use the protons directly from the proton driver. There would in principle be no limitations to using the full power of the driver.

Pion production peaks at low energy, so 8 GeV is preferred over 16 GeV. Furthermore, background from nu_e is reduced at lower energy because kaon production falls below threshold and is sharply suppressed. Mini-Boone would be optimal at 5-6 GeV. Speculation: one might be able to extract during acceleration, before 8 GeV is reached.

The project outlined below could be used as R&D for a neutrino factory, especially as regards target technology, and also horn technology. 1 MW at 15 Hz looks doable. Mini-Boone is 50 kW.

Physics.

Personal view: this project is worthwhile if there is a shot to see CPV in the neutrino sector. No other experiment can hope to do this. K2K can't do this physics because their nu_e contamination is too large. (Hence the need for a low energy proton driver, to shut off kaon production. The K2K protons are 12 GeV.)

Assume 1MW and conventional detector technology, though very large: 1000 kT*years. L = 150 km. (The K2K mass is 50 kTyr.)

Consider offsetting the detector from the neutrino centerline in order to subtend a lower-energy neutrino flux. Simulations indicate this may be very useful.

Energy spectra for signal and backgrounds are show. The visible energy is not very discriminating against nu_e contamination.

Result: one could see 28 signal on a background of 80. neutrino/anti-neutrino would come from switching the current in the horn.

Conclusion.

This physics is worthwhile. Although the scale of the detector is huge, it should be considered. No other experiment can do this, and the key is high flux and and low energy protons. Also, the time scale is right.