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39 items found (0 items not approved), displaying 1 to 10.[First/Prev] 1, 2, 3, 4 [Next/Last]

Instruments / Technical Area	Publication Details	Published
Mechanical Engineering	Programmable sled system for single bunch and multibunch linac operation C. Christou , P. Gu , A. Tropp LINAC2022 DOI: 10.18429/JACoW-LINAC2022-MOPOJO19 Open Access Show Abstract ▼ Abstract: The Diamond Light Source pre-injector linac generates single bunch and multibunch 100 MeV electron beams for top-up and fill of the storage ring. The linac is powered by two high-power 3 GHz klystrons, and both klystrons are required for reliable injection into the booster and storage ring. In order to introduce redundancy, a SLED pulse compression cavity has been installed so that the linac can operate from just one klystron, with the second klystron held as a standby. A simple phase flip can be used to generate a high-power transient RF spike, suitable for single bunch linac operation, and a programmable amplitude and phase drive profile can be specified to generate a constant-power klystron output suitable for multibunch operation. Details are presented of design, installation and high-power operation of the SLED system, and the ability to generate a long pulse, including corrections for klystron nonlinearity and deviations from modulator flat-top, is demonstrated.	Sep 2022
RF	RF plans for the Diamond-II upgrade C. Christou , P. Gu , Pe. Marten , S. A. Pande , A. Rankin IPAC2021 DOI: 10.18429/JACoW-IPAC2021-MOPAB107 Open Access Show Abstract ▼ Abstract: The RF system for the proposed Diamond-II upgrade will be based on normal-conducting EU HOM-damped cavities powered by high powered solid state amplifiers and controlled by digital low level RF systems built on the microTCA platform. Reasons for these design choices are discussed, and experience of the selected technologies in the Diamond-I ring are reviewed. The storage ring will also include a third harmonic cavity, and the different design options for this device are discussed. RF design of the booster ring is presented, and details are given of an upgraded linac and gun design intended to improve the charge delivered for top-up.	Aug 2021
RF	Overview of superconducting RF cavity reliability at Diamond Light Source C. Christou , P. Gu , P. Marten , S. A. Pande , A. Rankin , D. Spink , L. T. Stant , A. Tropp International Conference on RF Superconductivity (19th) DOI: 10.18429/JACoW-SRF2019-THP025 Open Access Show Abstract ▼ Abstract: Diamond Light Source has been providing beam for users since January 2007. The electron beam in the storage ring is normally driven by two superconducting CESR-B cavities, with two similar cavities available as spares. Day-to-day reliability of the cavities, measured by storage ring MTBF, has improved enormously over the years. A full analysis of how this improvement has been achieved is given, with particular attention paid to cavity voltage and vacuum pressure management, and the scheduling and procedure of cavity conditioning. The benefits and risks of full and partial warm-ups of the cavities are discussed, and details and impacts of cavity failure and repair are presented.	Aug 2019
Electrical Engineering	Simulation of cavity conditioning for the diamond SCRF cavity S. A. Pande , C. Christou , Pengda Gu 9th International Particle Accelerator Conference IPAC2018 DOI: 10.18429/JACoW-IPAC2018-WEPMF062 Open Access Show Abstract ▼ Abstract: Diamond SCRF cavities are pulse conditioned every week in order to keep them operating reliably. During conditioning, the cavities are detuned in order to sweep the standing wave through the waveguide. To match these cavities at lower voltage (typically < 1.4 MV) and at higher power, 3 stub tuners are used in the waveguide feed. Simulations with CST studio show that a strong SW field exists between the RF window and the matching posts. As the cavity is detuned the electric field maximum passes through the window causing heating of the ceramic. Temperature measurements with thermal camera reveal that the temperature of the window increases to maximum when the cavity is detuned towards higher frequency. Based on the simulation results and the measurements, it was decided to reduce the conditioning voltage. These results are summarised.	Jun 2018
RF	Commissioning of the hybrid superconducting/normal conducting RF system in the Diamond storage ring C. Christou , A. G. Day , P. Gu , P. J. Marten , S. A. Pande , D. Spink , A. Tropp 9th International Particle Accelerator Conference DOI: 10.18429/JACoW-IPAC2018-THPMF007 Open Access Show Abstract ▼ Abstract: Two 500 MHz HOM damped normal conducting cavities have been installed in the Diamond storage ring to ensure continuity of operation of Diamond in the event of a failure of one of the two existing superconducting cavities. Following receipt from the manufacturer, the cavities were incorporated into an assembly including vacuum pumping, cooling and interlocked diagnostics and then tested for vacuum integrity and RF performance. Both cavities were then conditioned up to high power in Diamond's RF test facility before being installed in the storage ring in August and November 2017. Conditioning and operation has been carried out using a new digital LLRF system. Results of acceptance tests and commissioning with power and beam are presented, together with the current status of the hybrid RF system and options for further improvement of the system in the near future.	Jun 2018
RF	Operation of Diamond superconducting RF cavities P. Gu , C. Christou , P. J. Marten , S. A. Pande , A. F. Rankin , D. Spink 8th International Conference on RF Superconductivity SRF2017 DOI: 10.18429/JACoW-SRF2017-MOPB016 Open Access Show Abstract ▼ Abstract: The Diamond Light Source storage ring has been in operation using superconducting RF cavities since 2007. Diamond has four superconducting cavity modules with two usually installed at any one time. The four cavities perform differently in many aspects such as reliable operating parameters and time in service, with the longest in continuous service for 7 years without failure and the shortest failing after only 8 months. All Diamond superconducting RF cavities suffered many fast vacuum trips in their early years, but after many years of efforts, the performance of the cavities have now been effectively managed by weekly conditioning, partial warm-up during shut down and cavity voltage level control. We will discuss our experience with superconducting RF cavities and our future plan.	Jan 2018
RF	Multipactor study in the coupler region of the Diamond SCRF cavities S. A. Pande , C. Christou , Pengda Gu , G. Burt 18th International Conference on RF Superconductivity SRF2017 DOI: 10.18429/JACoW-SRF2017-TUPB010 Open Access Show Abstract ▼ Abstract: The Diamond storage ring operates with two CESR-B type Superconducting RF cavities. The cavities suffer from trips with a sudden loss of accelerating field if operated above a certain voltage. Consequently the cavities are operated at voltages up to 1.4 MV for better reliability. These cavities are iris coupled and have fixed Qext. At these lower operating voltages, the optimum condition for beam loading is satisfied at powers around 100 kW. For operation at 300 mA with two cavities, the power needed per system exceeds 200 kW. Therefore 3 stub tuners are used to lower the Qext to move the optimum condition close to 200kW. Additionally, the step due to the difference in the height of the coupling waveguide on the cavity and that of the vacuum side waveguide on the window results in a standing wave between the cavity and the window even at matched operation. The 3 stub tuner further enhances this standing wave. Numerical simulation reveals that the standing wave field from the cavity penetrates into the coupling waveguide increasing the probability of multipactor and breakdown in the coupler region. The results of multipactor simulations in this region with CST Studio are discussed.	Jan 2018
Mechanical Engineering	Progress with the Diamond Light Source RF upgrade C. Christou , A. G. Day , M. J. Duignan , P. Gu , N. Hammond , P. Marten , S. A. Pande , D. Spink IPAC2017 DOI: 10.18429/JACoW-IPAC2017-THPIK112 Open Access Show Abstract ▼ Abstract: Failure of a superconducting cavity in the Diamond storage ring can lead to extended down-time because of the time required to remove the module from the ring, the inability to access the cavity without removal from the cryostat and the long time to repair of the module. To reduce the risk to storage ring operation, normal conducting cavities are being installed to support operation of the superconducting cavities. Two cavities will be introduced in 2017 and work is progressing with RF amplifiers, transmission lines and low-level RF as well as storage ring engineering and controls. A summary of progress so far is presented and the plan for installation and further RF upgrades is outlined.	May 2017
RF	Digital Low Level RF systems for Diamond Light Source Pengda Gu , C. Christou , I. Uzun , P. Hamadyk , A. Salom , F. Perez , E. Morales IPAC2017 DOI: 10.18429/JACoW-IPAC2017-THPAB152 Open Access Show Abstract ▼ Abstract: Analogue low level RF (LLRF) systems have been used to date for both Diamond storage ring and booster RF cavities. They have been in operation for nearly ten years without a major problem. However, digital LLRF can offer new desirable functionalities such as fast data logging, 'probe blip' blockage and automation of routine tasks. Better performance is also envisaged with up to date hardware. A digital LLRF system has been developed with Alba Synchrotron as a common platform for the storage ring and booster, including superconducting and normal conducting RF cavities. The new digital LLRF is based on Virtex6 FPGA and fast ADCs and DACs. One system has been built and verified in the Diamond booster with beam. The design will be implemented for all other Diamond RF cavities.	May 2017
Mechanical Engineering	Electron beam commissioning of the DDBA modification to the Diamond storage ring I. P. S. Martin , M. Apollonio , C. P. Bailey , C. Christou , R. T. Fielder , M. J. Furseman , E. Koukovini-Platia , T. Pulampong , G. Rehm , W. Rogers , B. Singh , R. Bartolini IPAC2017 DOI: 10.18429/JACoW-IPAC2017-WEPAB095 Open Access Show Abstract ▼ Abstract: The Diamond storage ring has been modified by replacing one of the existing double bend achromat (DBA) cells with a double-DBA (DDBA) cell*. This change represents the largest modification to the storage ring since it was first commissioned in 2006, and was installed and fully commissioned during a single 8 week shutdown in autumn 2016. In view of this tight schedule, the planned commissioning steps and all high-level software needed to be developed and thoroughly tested in advance. Electron beam commissioning occupied the final 2 weeks of the shutdown, during which the injected electrons were captured and accumulated, the correct linear lattice was established, the nonlinear beam dynamics were studied, IDs were closed and the target 300 mA was achieved. This paper presents an overview of these activities.	May 2017

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