This work describes first commissioning results from the Cornell Brookhaven Energy Recovery Test Accelerator Fractional Arc Test. These include the recommissioning of the Cornell photo-injector, the first full energy operation of the main linac with beam, as well as commissioning of the lowest energy matching beamline (splitter) and a partial section of the Fixed Field Alternating gradient (FFA) return loop featuring first production Halbach style permanent magnets. Achieving these tasks required characterization of the injection beam, calibration and phasing of the main linac cavities, demonstration of the required 36 MeV energy gain, and measurement of the splitter line horizontal dispersion and R56 at the nominal 42 MeV. In addition, a procedure for determining the BPM offsets, as well as the tune per cell in the FFA section via scanning the linac energy and inducing betatron oscillations around the periodic orbit in the fractional arc was developed and tested. A detailed comparison of these measurements to simulation is discussed.

This document includes twelve sections related to the previous Fractional Arc Test (FAT), CBETA final installation plan has which follows the milestones signed in the contract with the New York State Energy Development Authority (NYSERDA). In the second part we provide a plan for final installation, hardware and software preparation and the beam commissioning.

As part of this development effort, the Cornell-BNL Energy recovery linac Test Accelerator (CBETA) [3], a 4-pass, 150 MeV energy recovery linac (ERL), utilizing a Non-scaling Fixed Field Alternating-gradient (NS-FFA) permanent magnet return loop, is currently under design and construction at Cornell University through the joint collaboration of Brookhaven National Lab (BNL) and the Cornell Laboratory for Accelerator based Sciences and Education (CLASSE). Building on the significant advancements in high-brightness photoelectron sources and SRF technology at Cornell, as well as the FFA magnet and lattice design expertise from BNL, CBETA will establish the operation of a multi-turn SRF based ERL utilizing a compact FFA return loop with large energy acceptance (a factor of roughly 3.6 in energy), and thus demonstrate one possible cost-reduction technology under consideration for the eRHIC design. Moreover, successful completion of the CBETA project requires the study and measurement of many critical phenomena relevant to designing the EIC: the Beam-Breakup (BBU) instability, halo-development and collimation, growth in energy spread from Coherent Synchrotron Radiation (CSR), and CSR micro bunching, and thus should provide valuable insight to the EIC and ERL communities. In order to demonstrate the viability of the CBETA design, the Fractional Arc Test (FAT) was added to the CBETA commissioning sequence.

In the framework of the ERL prototyping, Cornell University has built two cryomodules, one injector module and one prototype Main Linac Cryomodule (MLC). In 2015, the MLC was successfully cooled down for the first time. We will report details on the cool-down as well as cycle tests we did in order to achieve slow and fast cool-down of the cavities. We will also report on the improvement we made on the injector cryomodule which also included a modification of the heat exchanger can that allows now a more controlled cool-down, too.

A series of heat exchanger can (HXC) assemblies have been designed, constructed and built to utilize existing 4.2 K liquefaction and compressor capabilities to provide helium gas coolant streams of 80 K, 4.5 K, and liquid from 1.6 to 2.0 K for operating cryomodules containing from one to six superconducting RF cavities built for an energy recovery linear accelerator. Designs for the largest assemblies required up to 100 W of cooling at 1.8 K with precise temperature control, especially during cool-down, and up to 2000 W at 80 K (with a 40 K temperature rise). A novel feature of these assemblies was the use of relatively inexpensive brazed stainless steel plate heat exchangers intended for room-temperature operation with water or oil, but which in practice worked well at cryogenic temperatures. The choice of operating temperatures/pressures were to provide single-phase helium flow for better control of coolant distribution in the 80 K and 4.5 K streams, to take advantage of locally elevated heat capacity near the critical point for the 4.5 K stream, and in the region below 2 K to get the best possible Q from the niobium cavities under test.

This design report describes the construction plans for the world's first multi-pass SRF ERL. It is a 4-pass recirculating linac that recovers the beam's energy by 4 additional, decelerating passes. All beams are returned for deceleration in a single beam pipe with a large-momentum-aperture permanent magnet FFAG optics. Cornell University has been pioneering a new class of accelerators, Energy Recovery Linacs (ERLs), with a new characteristic set of beam parameters. Technology has been prototyped that is essential for any high brightness electron ERL. This includes a DC electron source and an SRF injector Linac with world-record current and normalized brightness in a bunch train, a high-current linac cryomodule, and a high-power beam stop, and several diagnostics tools for high-current and high-brightness beams. All these are now being used to construct a novel one-cryomodule ERL in Cornell's Wilson Lab. Brookhaven National Laboratory (BNL) has designed a multi-turn ERL for eRHIC, where beam is transported more than 20 times around the 4km long RHIC tunnel. The number of transport lines is minimized by using two arcs with strongly-focusing permanent magnets that can control many beams of different energies. A collaboration between BNL and Cornell has been formed to investigate this multi-turn eRHIC ERL design by building a 4-turn, one-cryomodule ERL at Cornell. It also has a return loop built with strongly focusing permanent magnets and is meant to accelerate 40mA beam to 150MeV. This high-brightness beam will have applications beyond accelerator research, in industry, in nuclear physics, and in X-ray science.

High-power, high-brightness electron beams are of interest for many applications, especially as drivers for free electron lasers and energy recovery linac light sources. For these particular applications, photoemission injectors are used in most cases, and the initial beam brightness from the injector sets a limit on the quality of the light generated at the end of the accelerator. At Cornell University, we have built such a high-power injector using a DC photoemission gun followed by a superconducting accelerating module. Recent results will be presented demonstrating record setting performance up to 65 mA average current with beam energies of 4–5 MeV.

A single-cavity horizontal test cryomodule (HTC) ha s been designed and fabricated recently at Cornell University for ERL project. This cryomodule is a shortened version of the full injector cryomodule, housing five superconducting cavities. It serves as a test bench for new design features and for testing fully dressed t wo-cell ERL injector cavities. The cryostat design has been optimized for precise cavity alignment, good magnet ic shielding, and high cryogenic loads from the RF cav ities, input couplers, and HOM loads. The HTC was made long enough so in the future it can accommodate longer, multicell cavities of the ERL main linac. In this p aper we report on results from the first full test of the H TC, including RF system and superconducting cavity performance, cryomodule studies and operation of a new 2 K cryogenic system.

A complete system for operating, protecting and monitoring a superconducting magnet is described. This system is used in CESR (Cornell Electron Storage Ring) at Cornell University's Laboratory for Elementary Particle Physics (LEPP) for the CESR superconducting wigglers, part of the accelerator upgrade in pursuit of the CESR charm physics program known as CESR-c [1].

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.