BNL, Upton, Long Island, New York
A new 3rd generation light source (NSLS-II project) is in the early stage of construction at Brookhaven National Laboratory. The NSLS-II facility will provide ultra high brightness and flux with exceptional beam stability. It presents several challenges in the diagnostics and instrumentation, related to the extremely small emittance. In this paper, we present an overview of all planned instrumentation systems, results from research & development activities; and then focus on other challenging aspects.
BNL, Upton, Long Island, New York
The reduction of beta* beyond the 1m design value at RHIC has been consistently achieved over the last 6 years of RHIC operations, resulting in an increase of luminosity for different running modes and species. During the recent 2007-08 deuteron-gold run the reduction to 0.70 from the design 1 m achieved a 30% increase in delivered luminosity. The key ingredients in allowing the reduction have been the capability of efficiently developing ramps with tune and coupling feedback, orbit corrections on the ramp, and collimation at injection and on the ramp, to minimize beam losses in the final focus triplets, the main aperture limitation for the collision optics. We will describe the operational strategy used to reduce the b*, at first squeezing the beam at store, to test feasibility, followed by the operationally preferred option of squeezing the beam during acceleration, and the resulting luminosity increase obtained in the Cu-Cu run in 2005, Au-Au in 2007 and the deuteron-Au run in 2007-08. We will also include beta squeeze plans and results for the upcoming 2009 run with polarized protons at 250 GeV.
BNL, Upton, Long Island, New York
Three-dimensional electromagnetic simulations have suggested a variety of measures to mitigate the problem of button BPM trapped mode heating. A test fixture, using a combination of commercial-off-the-shelf and custom machined components, was assembled to validate the simulations. We present details of the fixture design, measurement results, and a comparison of the results with the simulations.
BNL, Upton, Long Island, New York
The outer circumference of a BPM button and the inner circumference of the button housing comprise a transmission line. This transmission line typically presents an impedance of a few tens of ohms to the beam, and couples very weakly to the 50 Ω coaxial transmission line that comprises the signal path out of the button. The modes which are consequently excited and trapped often have quality factors of several hundred, permitting resonant excitation by the beam. The combination of short bunches and high currents found in modern light sources and colliders can result in the deposition of tens of watts of power in the buttons. The resulting thermal distortion is potentially problematic for maintaining high precision beam position stability, and in the extreme case can result in mechanical damage. We present here a simple algorithm that uses the input parameters of beam current, bunch length, button diameter, beampipe aperture, and fill pattern to calculate a figure-of-merit for button heating. Data for many of the world’s light sources and colliders is compiled in a table.
BNL, Upton, Long Island, New York
The thermal distortion resulting from BPM button trapped mode heating is potentially problematic for achieving the high precision beam position measurement needed to provide the sub-micron beam position stability required by light source users. We present a button design that has been thermo-mechanically optimized via material selection and component geometry to minimize this thermal distortion. Detailed electromagnetic analysis of the button geometry is presented elsewhere in these proceedings.
BNL, Upton, Long Island, New York
The NSLS-II Light Source being built at Brookhaven National Laboratory is expected to provide submicron stability of the electron orbit in the storage ring in order to utilize fully the very small emittances and electron beam sizes. This requires high stability supports for BPM pick-up electrodes, located near insertion device source. Description of the efforts for development of supports including carbon tubes and invar rods is presented.