Engineering topics

Shaftan, Timur

Publications and source records attributed to Shaftan, Timur.

45 records · Page 3

DOE OSTI2018

Modification of the Booster Extraction Straight Section

In the process of conceptual design of the NSLS-II booster we developed an extraction layout based on a single strong pulsed septum turning the beam outside the booster vacuum chamber. This layout may not be ideal since pulsed power supply is not reproducible and its shot-to-shot voltage fluctuations will lead to an increase in the effective emittance of the extracted beam. Alternative solution1 is to divide the extraction in two magnets – a weak pulsed magnet and a strong DC magnet. This concept has been implemented in the current extraction layout.

42 ENGINEERING↗

DOE OSTI2018

Concept of the Complex Bend

Modern synchrotron lattices follow Multi-Bend Achromat approach and realize low emittance by arranging small horizontal beta-function and dispersion in the bends. In this paper we propose another optics solution aimed to reach low emittance by using a lattice element that we named as “Complex Bend”. The Complex Bend corresponds to a strong alternate focusing distributed along the bend so to maintain the beta-function and dispersion oscillating at low values. Comprising the ring lattice out of Complex Bends instead of regular dipoles will minimize the Ң-function and reduce the horizontal emittance while localizing bending to a small fraction of the storage ring circumference. The latter should help to gain more space for Insertion Devices. In the following, we present the concept of Complex Bend, considerations on the choice of its optimal parameters, as well as, thoughts of its practical realization. This paper gives a snapshot where our current studies stand and does not pretend to be a complete description of the Complex Bend engineering design and integration of this element into a specific ring lattice.

36 MATERIALS SCIENCE↗

DOE OSTI2017

Operation of the NSLS-II Injector with a Lower Booster Injection Energy

The NSLS-II injector consists of a 200 MeV linac and a 3 GeV full-energy booster synchrotron. The linac contains five traveling-wave S-band accelerating structures driven by two high-power klystrons. Optimization of the NSLS-II injector has continued since user operation started in October 2014. Beam losses have been minimized by the injector tuning and stabilization, and high level software has been developed to characterize the booster and injection parameters. However, due to the recently increased frequency of klystrons arcing which shortens the lifetime of the klystron, operation of the linac with lowered klystron output power would allow injection to be maintained with fewer trips and extended lifetime of klystrons. Apart from the energy difference, the low energy klystron operation is quite similar to the nominal 200 MeV operation. Injection trials were carried out with scaled magnet settings of the linac, linac-to- booster (LtB) transport line, and the booster. The beam was successfully injected into the booster on May 31, 2017 at the low energy mode of the 170 MeV LtB injection. Overall transfer efficiency from the linac to the storage ring is identical to the standard 200 MeV operation. The 170 MeV injection mode has been adopted in NSLS-II user operation ever since the beam study. In the most recent injector studies on June 28 and July 3, 2017, the booster injection energy was further decremented to the final target value of 100 MeV via applying the same method established in the 170 MeV operation. The ultimate value of 100 MeV is determined by the special requirement of operating the injector at single klystron while repairing the other klystron or with two klystrons with significantly reduced outputs for the purpose of maximizing klystron lifetimes.

36 MATERIALS SCIENCE↗

DOE OSTI2016

Modeling of Transition Through Half-Integer Resonance

In our recent experiment we measured the increase in the betatron oscillation amplitude due to crossing half-integer resonance by the beam while it performed synchrotron oscillations at NSLS-II. In this note we derive solutions of the equation of motion for a particle crossing ½ resonance and check these numerically against analytic solutions for the static detuning. We start our derivation from the first principles, i.e. from the Hill’s equation.

36 MATERIALS SCIENCE↗

DOE OSTI2016

Initial performances of first undulator-based hard x-ray beamlines of NSLS-II compared to simulations

Commissioning of the first X-ray beamlines of NSLS-II included detailed measurements of spectral and spatial distributions of the radiation at different locations of the beamlines, from front-ends to sample positions. Additionally, comparison of some of these measurement results with high-accuracy calculations of synchrotron (undulator) emission and wavefront propagation through X-ray transport optics, performed using SRW code, is presented.

47 OTHER INSTRUMENTATION↗

DOE OSTI2016

Rapid Crossing of a Resonance During Tune Modulation by Synchrotron Oscillations

It had become a standard practice to constrain the particle’s tune footprint while designing the ring lattice so that the particle tunes fit between harmful resonances that limit ring dynamic aperture (DA). This approach, known as “tune confinement”, puts tight limits on the magnitude of the tune shifts with amplitude and with momentum. The latter requires labor-intensive optimization of the off-energy dynamic aperture and control over the corresponding tune footprint for the large energy deviations and is a prerequisite to achieving reasonable lifetime if it is dominated by the Touschek scattering. As nonlinearities of the modern ring lattices are much enhanced as compared with the previous generation of synchrotron light sources, it is becoming more and more difficult to keep the off-momentum tune footprint confined. While one could reach reasonable on-energy DA suitable for injection into the machine, the off-energy DA optimization is much more complex and needs to satisfy more constraints so to reach large energy acceptance and secure decent lifetime at the high ring current. In certain cases when the lattice solution with the confined off-energy tune footprint cannot be found, one may ask whether crossing of a resonance stopband from off-momentum particle will lead to loss of this particle. Intuitively, if the particle crosses the stopband quickly, one may expect that the betatron oscillation amplitude will not increase substantially thereby keeping the particle within the machine acceptance. At the same time the tight tolerances of the modern lattice elements as designed and produced afford much narrower resonance stopbands being compared with the machines built decades ago. Under these circumstances the question above may be asked as what are the conditions for operating a ring with a large chromatic tune footprint, which crosses resonances, while not observing particle losses. In this paper we try to answer the questions above by studying the model of a particle with large initial momentum deviation (as, for example, driven by the Touschek scattering event), which crosses stopband of a half-integer resonance while executing synchrotron oscillations in the highly chromatic ring lattice.

36 MATERIALS SCIENCE↗

DOE OSTI2015

Reviewed Approach to Defining the Active Interlock Envelope for Front End Ray Tracing

To protect the NSLS-II Storage Ring (SR) components from damage from synchrotron radiation produced by insertion devices (IDs) the Active Interlock (AI) keeps electron beam within some safe envelope (a.k.a Active Interlock Envelope or AIE) in the transverse phase space. The beamline Front Ends (FEs) are designed under assumption that above certain beam current (typically 2 mA) the ID synchrotron radiation (IDSR) fan is produced by the interlocked e-beam. These assumptions also define how the ray tracing for FE is done. To simplify the FE ray tracing for typical uncanted ID it was decided to provide the Mechanical Engineering group with a single set of numbers (x,x’,y,y’) for the AIE at the center of the long (or short) ID straight section. Such unified approach to the design of the beamline Front Ends will accelerate the design process and save valuable human resources. In this paper we describe our new approach to defining the AI envelope and provide the resulting numbers required for design of the typical Front End.

36 MATERIALS SCIENCE↗

DOE OSTI2015

NSLS-II SR Commissioning Report

The NSLS-II storage ring (SR) phase I commissioning has been successfully completed in May 12, 2014. In accordance to the project milestone, 25 mA average current was achieved in the storage ring with PETRA III 500 MHz 7-cell PETRA-III RF cavity but w/o ID’s and Landau cavities. In about 5 weeks we delivered a 3 GeV beam to the ring injection straight section, made the 1st turn around the ring, achieved hundreds of turns optimizing injection, stored beam having sextupoles and RF turned ON. Injection efficiency was achieved 95%, close orbit rms value is ~100 um, tune and chromaticity were measured and adjusted as desired, and beam lifetime was a few hours depending on the stored beam current. This report consists of a summary, a chronological part, the injector system performance in Ch3, SR commissioning experience in Ch4 and the outlook of remaining work in Ch5. The SR commissioning experience includes the software experience, hardware (timing, diagnostics, RF, vacuum, PS) operation experience, the strategy for initial injection beam to the stored beam, measurement of the linear optics and control to the desired value, nonlinear beam dynamics study, beam instability study, the subsystem reliability and fault study at different scenarios.

36 MATERIALS SCIENCE↗

DOE OSTI2015

NSLS-II Emittance and Lifetime with Damping Wigglers

This paper is focused on the measurements of the major machine parameters under influence of the Damping Wigglers and their comparison with analytic estimates. We present analysis of the impact of the Damping Wigglers on the beam emittance and lifetime in the NSLS-II storage ring. We conclude that these parameters for the NSLS-II follow well-known dependencies as described, for example, by Weidemann and Touschek. Appendices A and B show details of the experiment and the estimates.

36 MATERIALS SCIENCE↗