OSC Workshop Summary
W. Franklin ( 2-15-2006)
An Optical Stochastic Cooling (OSC) workshop was held at MIT-Bates on February 2,
2006, in order to explore the technical issues that would need to be addressed for
successfully mounting the experiment and to understand the benefit that would ensue for
the RHIC program. This synopsis will present the important points from the workshop
discussion and the next steps that need to be taken to move forward.
1) Calculations suggest OSC has the potential to yield significant improvements in
performance for RHIC and eRHIC through improvements in beam lifetime and
background reduction if technical challenges can be met. Benefits would be
greatest for protons and light ions, particularly if the cooling rate could be large
enough to match the growth in beam emittance from beam-beam interactions
which reduce the luminosity.
2) Optical stochastic cooling is largely complementary to electron cooling. OSC
would produce strongest cooling of the beam halo, while electron cooling is more
efficient in cooling at short distances, i.e. the core of the beam. Reduction of the
halo is of essential interest to both the STAR and PHENIX collaborations that are
developing silicon vertex tracking upgrades using sensors located very close to
the vertex to measure displaced vertices from decays of short-lived particles.
3) OSC may allow smaller emittance electron beams in storage rings. This could
have great potential for higher brightness light sources using electron storage
rings. This would be directly testable at Bates.
4) A demonstration experiment of OSC performed at Bates would further
development of the technique for use at higher-energy proton and ion machines.
As the operating cost for machines such as RHIC is high, the parallel
development of OSC at the available Bates accelerator is highly cost effective. In
particular, OSC at Bates would explore much of the beam physics but would have
far less stringent amplifier requirements and far lower cost. Such an experiment
would be tailored to study questions of interest to RHIC.
5) Much of the discussion pertained to necessary steps to mount an OSC
demonstration experiment at Bates on the shortest possible time scale. Steps
include a preliminary experimental feasibility study using the Bates South Hall
Ring and a parallel design study on development of the optical amplifier system.
6) Possibilities to both minimize the cost and reduce implementation time were
explored. These include reuse of existing components and designing an
operational schedule for the machine with other proposed accelerator physics
studies to minimize running time.
7) There is enormous synergy between the Bates THz and OSC proposals. This
includes many of the diagnostics and controls and studies of the orbit response.
1) The optimal energy to do the experiment needs to be determined. The effect of
Touschek (intrabeam) scattering which reduces the storage lifetime at lower
energy in the South Hall Ring (SHR) must be balanced vs. the benefit of lowering
the energy to yield a longer synchrotron radiation damping time to observe OSC.
These topics are being investigated by the Bates Accelerator Physics Group.
2) Several issues regarding configuration of the Bates accelerator complex to meet
the specific conditions for an OSC test must be explored experimentally during a
SHR feasibility study.
i. Control of the bunch filling pattern for SHR operation (underway)
ii. Performance of SHR diagnostics for fast profile monitoring
iii. Low current, few bunch operation of the SHR
iv. Beam profile optimization for OSC demo (transverse and longitudinal)
A test run as soon as possible is required to investigate these topics.
3) Reuse of existing undulators would produce significant cost savings for the
experiment. The properties of the undulators are somewhat flexible, but it is
important to have two which are identical. Furthermore, their properties will drive
the design of the rest of the components. All workshop participants agreed to
look for viable options, such as prototype or spare undulators from light sources.
4) Development of the optical amplifier is a tractable problem for the Bates
experiment. Required power levels and gain are somewhat lower than the original
estimates in the proposal and will simplify the design. Development of the
amplifier at the MIT Research Laboratory for Electronics (RLE) can proceed
independently of accelerator development. A rough estimate of 6 months to order
and assemble the amplifier was given.
5) The design and implementation of the bypass chicane is the greatest challenge of
the project. This requires only modest capital funds provided that many existing
magnets and power supplies from the decommissioned Bates Extraction Line are
utilized. The primary challenge is the realization of a highly isochronous design
which eliminates particle mixing in the bypass. The LBNL group has carried out
preliminary calculations for such a bypass. The system must be built to allow the
OSC system to be tuned with a small number of adjustable parameters.
Significant mapping of the bypass response using SHR kickers will be required.
6) Diagnostics and fast feedback present another significant challenge for the
experiment and an opportunity to significantly advance the field. Phase stability must be achieved between the delayed electron bunch and its amplified undulator radiation at the sub-micron level. Workshop participants with significant experience in microwave stochastic cooling emphasized the importance of a clean signal to indicate proper tuning of the OSC system. Interferometric techniques will be expensive and there was significant discussion on development of a direct diagnostic based on undulator or dipole edge radiation.
7) Simulation for the South Hall Ring could play an important role in development and analysis of the OSC experiment. A scientific computing collaboration between BNL and Bates has recently been forged for a SciDAC proposal.
Workshop on Optical Stochastic Cooling
February 2, 2006
MIT-Bates Accelerator Center
9:00 - Opening Remarks (R. Milner)
9:10 - Transit-Time Optical Stochastic Cooling (A. Zholents)
9:45 – The Optical Stochastic Cooling Program at BNL (V. Yakimenko)
10:45 – Coffee Break
11:00 – Optical Stochastic Cooling Proposal at MIT-Bates (W. Franklin)
11:45 – Optical Amplifier Development at MIT (F. Kaertner)
12:15 – Lunch served
13:00 – Visit to MIT-Bates South Hall Ring
13:30 – Discussion
15:15 – Coffee Break
15:30 – Working plan formation
16:30 - Adjourn
Participants in the Optical Stochastic Cooling workshop at MIT/Bates on 02/02/2006
Name Affilation email address
Taylan Akdogan MIT firstname.lastname@example.org Marcus Babzien BNL email@example.com Mike Blaskiewicz BNL firstname.lastname@example.org Mike Brennan BNL email@example.com
Dan Cheever MIT firstname.lastname@example.org Karen Dow MIT email@example.com
Manouchehr Farkhondeh MIT firstname.lastname@example.org Wolfram Fischer BNL email@example.com Bill Franklin MIT firstname.lastname@example.org Franz Kaertner MIT email@example.com Jan van der Laan MIT firstname.lastname@example.org Richard Milner MIT email@example.com
Thomas Roser BNL firstname.lastname@example.org
Aleem Siddiqui MIT email@example.com Stephen Steadman MIT firstname.lastname@example.org Chris Tschalaer MIT email@example.com Genya Tsentalovich MIT firstname.lastname@example.org Bill Turchinetz MIT email@example.com Defa Wang MIT firstname.lastname@example.org
Dong Wang MIT email@example.com Fuhua Wang MIT firstname.lastname@example.org
Vitaly Yakimenko BNL email@example.com Alexander Zholents LBL firstname.lastname@example.org Max Zolstorev LBL email@example.com