During the summer and fall of 2018 the Cornell High Energy Synchrotron Source (CHESS) is undergoing an upgrade to increase high-energy flux for x-ray users. The upgrade requires replacing one-sixth of the Cornell Electron Storage Ring (CESR), inverting the polarity of half of the CHESS beam lines, and switching to single-beam on-axis operation. The new sextant is comprised of six double-bend achromats (DBAs) with combined-function dipole-quadrupoles. Although the DBA design is widely utilized and well understood, the constraints for the CESR modifications make the CHESS-U lattice unique. This paper describes the design objectives, constraints, and implementation for the CESR accelerator upgrade for CHESS-U.

During the summer and fall of 2018 the Cornell High Energy Synchrotron Source (CHESS) is undergoing an upgrade to increase high-energy flux for x-ray users. The upgrade requires replacing one-sixth of the Cornell Electron Storage Ring (CESR), inverting the polarity of half of the CHESS beam lines, and switching to single-beam on-axis operation. The new sextant is comprised of six double-bend achromats (DBAs) with combined-function dipole-quadrupoles. Although the DBA design is widely utilized and well understood, the constraints for the CESR modifications make the CHESS-U lattice unique. This paper describes the design objectives, constraints, and implementation for the CESR accelerator upgrade for CHESS-U.

We developed, built and beam tested a novel, compact, in-vacuum undulator magnet based on an adjustable phase (AP) scheme. The undulator is 1 m long with a 5mm gap. It has a pure permanent magnet structure with 24.4mm period and 1.1 Tesla maximum peak field. The device consists of two planar magnet arrays mounted on rails inside of a rectangular box-like frame with 156 mm × 146 mm dimensions. The undulator magnet is enclosed in a 273 mm (10.75") diameter cylindrical vacuum vessel with a driver mechanism placed outside. In May 2012 the CHESS Compact Undulator (CCU) was installed in Cornell Electron Storage Ring and beam tested. During four weeks of dedicated run we evaluated undulator radiation properties as well as magnetic, mechanical and vacuum properties of the undulator magnet. We also studied the effect of the CCU on storage ring beam. The spectral characteristics and intensity of radiation were found to be in very good agreement with expected. The magnet demonstrated reproducibility of undulator parameter K at 1.4 × 10−4 level. It was also found that the undulator K. parameter change does not affect electron beam orbit and betatron tunes.

Energy-Recovery Linacs (ERLs) are proposed as drivers for hard x-ray sources because of their ability to produce electron bunches with small, flexible cross sections and short lengths at high repetition rates. Cornell University has pioneered the design and hardware for ERL lightsources. This preparatory research for ERL-lightsource construction will be discussed. Important milestones have been achieved in Cornell’s prototype ERL injector, including the production of a prototype SRF cavity that exceeds design specifications, the regular production of long-lived and low emittance cathodes, the acceleration of ultra-low emittance bunches, and the world-record of 65 mA current from a photoemission DC gun. We believe that demonstration of the practical feasibility of these technologies have progressed sufficiently to allow the construction of an ERLbased lightsource like that described in Ref [1].

We developed, built and beam tested a novel, compact, in-vacuum undulator magnet based on an adjustable phase (AP) scheme. The undulator is 1 m long with a 5mm gap. It has a pure permanent magnet structure with 24.4mm period and 1.1 Tesla maximum peak field. The device consists of two planar magnet arrays mounted on rails inside of a rectangular box-like frame with 156 mm x 146 mm dimensions. The undulator magnet is enclosed in a 273 mm (10.75”) diameter cylindrical vacuum vessel with a driver mechanism placed outside. In May 2012 the CHESS Compact Undulator (CCU) was installed in Cornell Electron Storage Ring and beam tested. During four weeks of dedicated run we evaluated undulator radiation properties as well as magnetic, mechanical and vacuum properties of the undulator magnet. We also studied the effect of the CCU on storage ring beam. The spectral characteristics and intensity of radiation were found to be in very good agreement with expected. The magnet demonstrated reproducibility of undulator parameter K at 1.4 x10 -4 level. It was also found that the undulator K parameter change does not affect electron beam orbit and betatron tunes.

Cornell University has built a high average current electron injector for use with an Energy Recovery Linac. The injector is designed for up to 100 mA average current at 5 MeV (33 mA at 15 MeV) and is expected to produce the ultra-low emittances needed for an ERL. An overview of the initial performance of this injector, the status of beam commissioning, and a summary of experiments being undertaken to demonstrate low emittance and high average current are presented.

Cornell University is planning to build an Energy Recovery Linac (ERL) X-ray facility. For an ERL, it is well known that the x-ray beam brightness for the users is mainly determined by the initial electron beam emittance provided by the injector. To address technical challenges of producing very low emittance beams at high average current as required for an ERL, Cornell University has proposed a prototype injector with 5-15 MeV beam energy, 100 mA maximum average current and 77 pC/bunch. In this article, we describe the design, construction and initial results for an ERL injector prototype now under operation.

CESR-c operates with twelve 2.1 tesla wigglers that account for 90% of the synchrotron radiation with beam energy in the range of 1.8 to 2.1 GeV. The wigglers reduce the radiation damping time from 0.5 seconds to 50 milliseconds. The carefully designed wigglers restrict neither physical nor dynamic aperture of the storage ring though both quadrupole and sextupole distributions must be tailored to compensate the primary optics effects of the wigglers. Colliding beam performance limits are determined by the numerous parasitic beam-beam interactions in the single ring. Several approaches taken to mitigate these limiting effects are described herein. The CESR-c wigglers are an excellent match to the requirements for future damping rings. Flexible optics, extensive infrastructure, and resource expertise, form an effective test bed for assessment and solution of damping ring issues such as electron cloud and ion effects, and exploring ultra-low emittance beams.

A luminosity monitor using photons from radiative bhabha events at the CLEO interaction point (IP) has been installed in the Cornell Electron Storage Ring (CESR) [1]. A key vacuum and detector component is the photon window/converter whose uniformity and thickness are critical for determining the resolution of the total energy deposited in the segmented luminosity monitor. The window design must accommodate the operational requirements of the new monitor at CLEO-c beam energies of 1.5-2.5 GeV and also provide sufficient safety margin for operation at 5.3 GeV beam energies for Cornell High Energy Synchrotron Source (CHESS) running. During 5.3 GeV operation, intense stripes of synchrotron radiation (SR) from the interaction region (IR) superconducting quadrupole magnets (SC Quads) as well as nearby bending magnets strike the window. During the course of window development, several materials and designs were considered. Thermal stresses were calculated using ANSYS for various beam conditions to guide the cooling design. A window using aluminum (Al) alloy 6061-T6 was ultimately chosen to provide optimal performance for both CLEO-c and CHESS running conditions. The window has been in successful operation since September 2004.

The Introduction to this paper summarizes the history of the Global Accelerator Network (GAN) concept and the recent workshops that discussed the relationship between GAN and Remote Operations. The Remote Operations Scenarios section brings out the organizational philosophy embodied in GAN-like and to non-GAN-like scenarios. The set of major Topics Raised at the Workshops are only partially resolved. Collaboration Tools are described and discussed, followed by examples of Remote Accelerator Control Projects around the world.

After construction of a prototype unit, five additional wiggler magnets for the CESR-c conversion have been completed at a rate exceeding one per month. These 2.1 T superferric magnets are built and assembled primarily in house with a minimal staff. We describe the general design and fabrication methods for these magnets. An additional 10 magnets will be constructed to complete the complement in the ring plus two spare units.

As part of the "CESR-c" upgrade project, a full-scale prototype superferric wiggler module has been installed into the Cornell Electron Storage Ring (CESR) and successfully operated since October 2002. At least eleven more wigglers are to be installed to enable full operation of the CESR-c. The wiggler magnets are chosen to achieve the necessary damping for optimum operation of CESR-c at a beam energy of 1.88 GeV. The wiggler cryostat units are designed to be modular, of fixed length flange-to-flange, so that they can be easily installed and exchanged. The cryostat incorporates several novel features including a suspension system with very low heat leak that prevents any significant motion during cool down, a custom triple cryogenic feedthrough, and a helium vessel made in two halves, each enclosing a half-magnet. This article presents the design, fabrication, and operation of the CESR-c wiggler cryostat.

We present a detailed design for operation of the Cornell Electron Storage Ring, CESR, in the energy range covering the /spl psi/ resonances and the Charm and Tau thresholds, as well as reaching to the upper Y resonances near 11 GeV. The addition of 18 m of super-ferric wiggler magnets will partially restore low energy beam emittance and damping times. Installation of superconducting quadrupoles in the interaction region and the addition of high performance superconducting RF cavities will enhance performance at all energies. Studies of optics, beam dynamics, wiggler and vacuum system performance, beam stability, and beam-beam effects confirm operation with a luminosity of 3/spl times/ 10/sup 32/ CM/sup -2/ sec/sup -1/ at 1.88 GeV.

As part of the Phase III luminosity upgrade, the Cornell Electron-Positron Storage Ring (CESR) RF system has been upgraded from normal conducting (NRF) to superconducting (SRF) cavities. The new superconducting cavities change the overall impedance of CESR and thus change the longitudinal bunch distribution. Measurements of the single bunch longitudinal distribution have been made using a streak camera on CESR with the SRF cavities present. These measurements are compared with earlier measurements on CESR with the NRF cavities. The CESR vacuum chamber impedance is determined from the current dependence of the single bunch charge distribution

We present a status report on the investigation of the Mobius scheme for producing equal-emittance round beams at CESR. An insert has been constructed with six 45/spl deg/ rotated quadrupoles which interchange horizontal and vertical betatron oscillations on each passage. We describe the single-beam dynamics and the limitations introduced by the chromaticity correcting sextupoles. We also report on our two-beam experience.

The Cornell electron-positron storage ring (CESR) luminosity has increased by a factor of >3 over the last 3 years with a peak luminosity of 8.0/spl times/10/sup 32/ cm/sup -2/ sec/sup -1/ and a record integrated luminosity of 750 pb/sup -1/ for one month. This increase in luminosity is in part due to improved alignment of magnetic elements. Operation with a pretzel orbit in multiple bunch mode places particular importance on alignment because of the side effects of magnetic correctors. We report the improvements in alignment and estimate the effects on colliding beam performance.

The Cornell electron storage ring (CESR) phase-III upgrade plan includes very strong permanent magnet quadrupoles in front of the cryostat for the superconducting quadrupoles and physically as close as possible to the interaction point. Together with the superconducting quadrupoles, they provide tighter vertical focusing at the interaction point. The quadrupoles are built with neodymium iron boron (NdFeB) material and operate inside the 15 kG solenoid field. Requirements on the field quality and stability of these quadrupoles are discussed and test results are presented.

Using the silicon strip detector of the CLEO experiment operating at the Cornell Electron-Positron Storage Ring (CESR), we have observed that the horizontal size of the luminous region decreases in the presence of the beam-beam interaction from what is expected without the beam-beam interaction. The dependence on the bunch current agrees with the prediction of the dynamic beta effect. This is the first direct observation of the effect.

The CESR Phase-III upgrade plan includes very strong permanent magnet quadrupoles in front of the cryostat for the superconducting quadrupoles and physically as close as possible to the interaction point. Together with the superconducting quadrupoles, they provide tighter vertical focusing at the interaction point. The quadrupoles are built with Neodymium Iron Boron (NdFeB) material and operate inside the 15 kG solenoid field. Requirements on the field quality and stability of these quadrupoles are discussed and test results are presented.