Full Energy Injection Research Articles

Optimization of an Interaction Region Quadrupole Magnet for a Future Electron-Ion Collider at JLab

The Jefferson Lab Electron Ion Collider (JLEIC) is a proposed new machine for nuclear physics research. It uses the existing CEBAF accelerator as a full energy injector to deliver 3 to 11 GeV electrons into a new electron collider ring. An all new ion accelerator and collider complex will deliver up to 200 GeV protons. The machine has luminosity goals of 1034cm−2 sec−1. The whole detector region including forward detection covers about 80 meters of the JLEIC complex. The lattice file for the machine has changed to accommodate the higher energy; this change requires all the magnets in the interaction region to change. This paper will describe the requirements for both the ion and electron beam superconducting magnets around the interaction point. All the Final Focusing Quadrupole (FFQ) magnets now have preliminary designs. This paper will describe the optimization process for one of these FFQs. The optimization is performed using the optimization module of SIMULIA Opera FEA and compared with ROXIE. An analytical design tool has also been developed to estimate the peak field in the coils. The quadrupole has been optimized for peak field in the coils, and magnetic length.

Preliminary Design of the Interaction Region Beam Transport Systems for JLEIC

The Jefferson Lab Electron Ion Collider (JLEIC) is a proposed new machine for a nuclear physics research. As proposed, it will deliver between 15 and 65 GeV center of mass energy collisions between electrons and nuclei. It uses the existing CEBAF accelerator as a full energy injector to deliver 3-10 GeV electrons into a new electron collider ring. An all new ion accelerator and collider complex will deliver up to 100 GeV protons, or 40 GeV/nucleon ions. The machine will have luminosity goals of above 10 33 cm -2 sec -1 in the whole energy range. The two collider rings use a unique figure eight layout to deliver a high degree of polarization in both beams. The machine will ultimately include room for two interaction regions. The crossing angle in the primary interaction region will be 50 mrad. This paper will describe the requirements and preliminary designs for both the ion and electron beam transport systems in the most complex 32 m region around the interaction point. The beam transport system includes three separate cryostats housing over 37 superconducting magnets operating at 4.5 K. The design of these cryostats must be closely integrated with the elements of the JLEIC detector.

Conceptual Design of the Interaction Region Magnets for Future Electron-Ion Collider at Jefferson Lab

The JLEIC is a proposed new machine for nuclear physics research. As designed, it will deliver from 15 and 65 GeV center of mass energy collisions between electrons and nuclei. It uses the existing CEBAF accelerator as a full energy injector to deliver electrons into a new electron collider ring. A new ion accelerator and collider complex will deliver up to 100 GeV protons, or 40 GeV/nucleon ions. The machine will have luminosity goals of above 10 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">33</sup> cm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">-2</sup> s <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">-1</sup> in the whole energy range with a maximum of a few 10 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">34</sup> cm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">-2</sup> s <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">-1</sup> . The machine has room for two interaction regions with only one initially installed. The crossing angle in the primary interaction region will be 50 mrad. The whole detector region including forward detection covers about 80 m of the JLEIC complex. This paper will describe the requirements and preliminary designs for both the ion and electron beam magnets in the complex 32-m-long interaction region around the interaction point. The interaction region has over 37 superconducting magnets operating at 4.5 K; these include dipoles, quadrupoles, skew-quadrupoles, solenoids, horizontal and vertical correctors, and higher order multipole magnets. The paper will also discuss the electromagnetic interaction between these magnets.

New features of the MAX IV thermionic pre-injector

The MAX IV facility in Lund, Sweden consists of two storage rings for production of synchrotron radiation. The smaller 1.5GeV ring is presently under construction, while the larger 3GeV ring is being commissioned. Both rings will be operating with top-up injections from a full-energy injector. During injection, the electron beam is first delivered to the main injector from a thermionic pre-injector which consists of a thermionic RF gun, a chopper system, and an energy filter. In order to reduce losses of high-energy electrons along the injector and in the rings, the electron beam provided by the thermionic pre-injector should have the correct time structure and energy distribution. In this paper, the design of the MAX IV thermionic pre-injector with all its sub components is presented. The electron beam delivered by the pre-injector and its dependence on parameters such as optics, cathode temperature, and RF power are studied. Measurements are here compared with simulation results obtained by particle tracking and electromagnetic codes. The chopper system is described in detail, and different driving schemes that optimize the injection efficiency for the two storage rings are investigated. During operation, it was discovered that the structure of the beam delivered by the gun is affected by mode beating between the accelerating and a low-order mode. This mode beating is also studied in detail. Finally, initial measurements of the electron beam delivered to the 3GeV ring during commissioning are presented.

Shielding NSLS-II light source: Importance of geometry for calculating radiation levels from beam losses

Third generation high brightness light sources are designed to have low emittance and high current beams, which contribute to higher beam loss rates that will be compensated by Top-Off injection. Shielding for these higher loss rates will be critical to protect the projected higher occupancy factors for the users. Top-Off injection requires a full energy injector, which will demand greater consideration of the potential abnormal beam miss-steering and localized losses that could occur. The high energy electron injection beam produces significantly higher neutron component dose to the experimental floor than a lower energy beam injection and ramped operations. Minimizing this dose will require adequate knowledge of where the miss-steered beam can occur and sufficient EM shielding close to the loss point, in order to attenuate the energy of the particles in the EM shower below the neutron production threshold (<10MeV), which will spread the incident energy on the bulk shield walls and thereby the dose penetrating the shield walls. Designing supplemental shielding near the loss point using the analytic shielding model is shown to be inadequate because of its lack of geometry specification for the EM shower process. To predict the dose rates outside the tunnel requires detailed description of the geometry and materials that the beam losses will encounter inside the tunnel. Modern radiation shielding Monte-Carlo codes, like FLUKA, can handle this geometric description of the radiation transport process in sufficient detail, allowing accurate predictions of the dose rates expected and the ability to show weaknesses in the design before a high radiation incident occurs. The effort required to adequately define the accelerator geometry for these codes has been greatly reduced with the implementation of the graphical interface of FLAIR to FLUKA. This made the effective shielding process for NSLS-II quite accurate and reliable. The principles used to provide supplemental shielding to the NSLS-II accelerators and the lessons learned from this process are presented.

Shielding synchrotron light sources: Advantages of circular shield walls tunnels

Third generation high brightness light sources are designed to have low emittance and high current beams, which contribute to higher beam loss rates that will be compensated by Top-Off injection. Shielding for these higher loss rates will be critical to protect the projected higher occupancy factors for the users. Top-Off injection requires a full energy injector, which will demand greater consideration of the potential abnormal beam miss-steering and localized losses that could occur. The high energy electron injection beam produce significantly higher neutron component dose to the experimental floor than lower energy injection and ramped operations. High energy neutrons produced in the forward direction from thin target beam losses are a major component of the dose rate outside the shield walls of the tunnel. The convention has been to provide thicker 90° ratchet walls to reduce this dose to the beam line users. We present an alternate circular shield wall design, which naturally and cost effectively increases the path length for this forward radiation in the shield wall and thereby substantially decreasing the dose rate for these beam losses. This shield wall design will greatly reduce the dose rate to the users working near the front end optical components but will challenge the beam line designers to effectively utilize the longer length of beam line penetration in the shield wall. Additional advantages of the circular shield wall tunnel are that it's simpler to construct, allows greater access to the insertion devices and the upstream in tunnel beam line components, as well as reducing the volume of concrete and therefore the cost of the shield wall.

Present status of the electron beam diagnostics system of the PLS-II linac

The PLS-II, the upgraded PLS (Pohang Light Source), has been providing users with photon beams in the top-up mode since March 2013. The requirements for the PLS-II linac to achieve the top-up injection are very demanding because it is a full energy injector with a very limited energy margin. One of the requirements is to ensure high injection efficiency in order to minimize the beam loss at the storage ring injection point and the experimental hall during injection because loss leads to a high radiation level in the experimental hall. The energy stability and energy spread of the accelerated electron beam are fundamental parameters to monitor and manage for high injection efficiency. An energy feedback system consisting of a stripline-type beam position monitor and the last klystron was implemented. To diagnose the injected beam’s energy and energy spread in real time during top-up mode injection, we installed an optical transition radiation (OTR) monitor system upstream of the beam transport line (BTL) after the first bending magnet. The energy and the energy spread ranges can be controlled with a horizontal slit installed after the OTR monitor. The vertical beam size of the accelerated beam must be decreased for efficient injection because the electron beam is injected into the storage ring with many in-vacuum undulators of small gaps. For this purpose, two vertical slits were installed in the BTL region. We will describe mainly those instruments closely related to top-up operation, though other beam diagnostic instruments have been used since PLS.

The MAX IV storage ring project.

The MAX IV facility, currently under construction in Lund, Sweden, features two electron storage rings operated at 3 GeV and 1.5 GeV and optimized for the hard X-ray and soft X-ray/VUV spectral ranges, respectively. A 3 GeV linear accelerator serves as a full-energy injector into both rings as well as a driver for a short-pulse facility, in which undulators produce X-ray pulses as short as 100 fs. The 3 GeV ring employs a multibend achromat (MBA) lattice to achieve, in a relatively short circumference of 528 m, a bare lattice emittance of 0.33 nm rad, which reduces to 0.2 nm rad as insertion devices are added. The engineering implementation of the MBA lattice raises several technological problems. The large number of strong magnets per achromat calls for a compact design featuring small-gap combined-function magnets grouped into cells and sharing a common iron yoke. The small apertures lead to a low-conductance vacuum chamber design that relies on the chamber itself as a distributed copper absorber for the heat deposited by synchrotron radiation, while non-evaporable getter (NEG) coating provides for reduced photodesorption yields and distributed pumping. Finally, a low main frequency (100 MHz) is chosen for the RF system yielding long bunches, which are further elongated by passively operated third-harmonic Landau cavities, thus alleviating collective effects, both coherent (e.g. resistive wall instabilities) and incoherent (intrabeam scattering). In this paper, we focus on the MAX IV 3 GeV ring and present the lattice design as well as the engineering solutions to the challenges inherent to such a design. As the first realisation of a light source based on the MBA concept, the MAX IV 3 GeV ring offers an opportunity for validation of concepts that are likely to be essential ingredients of future diffraction-limited light sources.

Top-up operation at Pohang Light Source-II.

After three years of upgrading work, PLS-II (S. Shin, Commissioning of the PLS-II, JINST, January 2013) is now successfully operating. The top-up operation of the 3 GeV linear accelerator had to be delayed because of some challenges encountered, and PLS-II was run in decay mode at the beginning in March 2012. The main difficulties encountered in the top-up operation of PLS-II are different levels between the linear accelerator and the storage ring, the 14 narrow gap in-vacuum undulators in operation, and the full energy injection by 3 GeV linear accelerator. Large vertical emittance and energy jitter of the linac were the major obstacles that called for careful control of injected beam to reduce beam loss in the storage ring during injection. The following measures were taken to resolve these problems: (1) The high resolution Libera BPM (see http://www.i-tech.si) was implemented to measure the beam trajectory and energy. (2) Three slit systems were installed to filter the beam edge. (3) De-Qing circuit was applied to the modulator system to improve the energy stability of injected beam. As a result, the radiation by beam loss during injection is reduced drastically, and the top-up mode has been successfully operating since 19th March 2013. In this paper, we describe the experimental results of the PLS-II top-up operation and the improvement plan.

Design of a low-emittance lattice for 3.5 GeV synchrotron light source

We investigate a lattice design for a low-emittance, high-brilliance intermediate energy synchrotron light source that is being intensively performed in the world. We present the design results in detail for a non-achromatic double bend achromat lattice with an emittance of 1.1 nm and 597.6 m circumference. Each superperiod has 4 straight sections, 7 m, 5.4 m, and 2 × 2.8 m in length, giving a total of 60 straight sections in the ring. The lattice is designed to be flexible and also provides an achromatic optics with an emittance of 3.2 nm. The lattice provides high brilliance at a photon energy of a few tens of keV, which meets the requirements of hard X-ray synchrotron radiation users. We investigated the dynamic aperture in the lattice with machine errors using a simulation method that achieves the optimal tune for the ring. The low-emittance lattice provides sufficient dynamic aperture after closed orbit distortion correction. We show an estimate of variations of emittance, energy spread, and dynamic aperture due to a wiggler in the straight sections. We present the design of an injection scheme for full energy injection, the space allocation in injection section, and the particle dynamics of injected beam. Particle tracking after beam injection was performed to examine the validity of the injection scheme. Our design lattice shows good optimization in terms of the emittance, number of straight sections, brilliance, and circumference as a light source for 3.5 GeV beam energy.

Impact of the Lambertson septum magnet on the photon beam flux in the PLS-II beam line experiment

The Pohang Light Source II (PLS-II) has been operating successfully since the completion on March 21, 2012 of the PLS-II project to upgrade the PLS. Because top-up injection is becoming a general operation mode in the 3 rd generation light source, top-up operation using full energy injection from the 3 GeV linear accelerator is one of the main goals of the PLS-II. In the PLS-II topup operation, small beam loss of the injected beam in the storage ring and stored beam oscillation during injection are two main issues to be solved. The top-up mode has been successfully operated since March 19, 2013, because the beam loss of injected beam in the storage ring was reduced. As a result, the flux stability, excepting injection time, in the beam line has been dramatically improved. During injection, a systematic dip pattern occurs in the photon beam flux due to oscillation of the vertical stored beam. The main source of the oscillation of the vertical stored beam is the leakage field of Lambertson septum magnet. In this paper, the impact of lambertson septum magnet on the stored beam oscillation will be described and an improvement plan will be presented.

Tracking study of transient behaviors at beam injection of the PLS-II ring

The PLS-II project to upgrade the Pohang Light Source (PLS) has been completed. In PLS-II, top-up operation with full energy injection from a 3 GeV linear accelerator is planned. Therefore, detailed studies of transient behaviors at beam injection are required. This paper present the results of a simulation study of PLS-II beam dynamics at beam injection. Particle tracking software, ELEGANT, was used to study several useful and interesting effects at beam injection. The timing and the energy of the injected beam and the error allowance tolerance of the kickers were investigated. Based on simulation results, the commissioning was successfully carried out, and the results will be described in this paper.

Ground design of a 3 GeV accelerator-complex for the synchrotron light in Tohoku, Japan (SLiT-J)

A conceptual design of 3 GeV accelerator complex for synchrotron radiation facility in Tohoku area, Japan (SLiT-J) is described. The complex is consisted with a 3 GeV low emittance storage ring and a C-band full-energy injector linac. Circumference of the ring should not be exceeded 300 m because of compactness (saving cost and power consumption). Nevertheless target emittance of the ring is less than 2 nmrad, which will be really competitive with newly constructed 3rd generation light sources. Tentatively designed lattice offers a low emittance of 1.8 nmrad with reasonably wide dynamic aperture. Presuming 4 typical undulators to cover the wide spectral range such as 10 eV to 20keV, the brightness is expected from 1017 – 1021 phs/mm2/mrad2/s/0.1%b.w./300mA. For the hard x-ray region, considerable photon flux may be provided by using multipole mini-wiggler with high magnetic field, which is inserted into the middle of cell. Though realistic prospect of the project is not predictable at present, we anticipate that the facility will be open in 2016.

Ramping study at the PLS-II storage ring

PLS-II (the upgrade of the Pohang Light Source) has been operated successfully since 21 March 2012. Since a 3-GeV linear accelerator is used as a full-energy injector, the performance of the linear accelerator is critical for reliable user service. Although the PLS-II linear accelerator has shown full reliability without interrupting user service during the first half year, there is always the possibility for failure of the 3-GeV linear accelerator system. For instance, any of the many pulsed high-power supplies may fail. Therefore, the storage ring should be prepared for injection at energies lower than 3-GeV. For that, we performed ramping studies, and we describe the results in this paper.

Pulsed sextupole injection for Sweden’s new light source MAX IV

The MAX IV facility presently under construction will include two storage rings for the production of synchrotron radiation. Both rings will be operated at a constant 500 mA of stored current with top-up shots supplied by the MAX IV linac acting as a full-energy injector. Until recently, injection into both storage rings was designed using a conventional approach: a closed four-kicker injection bump brings the stored beam to the septum blade where the injected bunches are captured in a single turn. This method, although commonly found in third generation light sources, has significant disadvantages. Therefore, an alternative injection into the storage rings using pulsed multipoles has been investigated. This type of injection does not require an injection bump and has the potential to make top-up injection fully transparent to users. Design studies have been successfully completed and as a consequence it has been decided to replace the originally foreseen conventional injection scheme with pulsed multipole injection in both MAX IV storage rings. This paper reports on these studies, presents pulsed sextupole injection schemes, and summarizes requirements for the pulsers, sextupole magnets, and vacuum chambers.

Sorting of bending magnets for the SSRF booster**Supported by SSRF Project

The Shanghai Synchrotron Radiation Facility (SSRF)booster ring, a full energy injector for the storage ring, is deigned to accelerate the electron beam energy from 150 MeV to 3.5 GeV that demands high extraction efficiency at the extraction energy with low beam loss rate when electrons are ramping. Closed orbit distortion (COD) caused by bending magnet field uniformity errors which affects the machine performance harmfully could be effectively reduced by bending magnet location sorting. Considering the affections of random errors in measurement, both ideal sorting and realistic sorting are studied based on measured bending magnet field uniformity errors and one reasonable combination of bending magnets which can reduce the horizontal COD by a factor of 5 is given as the final installation sequence of the booster bending magnets in this paper.

Facility Updates: Fermi @ Elettra: A Free Electron Laser for EUV and Soft X-ray Radiation

Sincrotrone Trieste has received funding and has begun the final refinement of technical parameters as well as the construction of a new Free Electron Laser (FEL) called Fermi. The new light source will be located adjacent to the existing Elettra storage ring and will use the linac that presently injects electrons into this light source. The linac will shortly become fully available to the Fermi project as a new dedicated full energy injection system is also being built for Elettra. Why are VUV and X-ray FELs so important and how do they work? Most readers will know that in a bending magnet, synchrotron radiation is created by the incoherent emission of each electron as it moves in a magnetic field.

Dependence of Dynamic Aperture on Betatron Tune at 2.5 GeV Pohang Light Source Storage Ring

The Pohang Light Source (PLS) storage ring is a synchrotron light source that has been operated using a 2.5 GeV full energy injection from a linac since October 2002. It is necessary to search for betatron tunes that can realize large dynamic apertures in a 2.5 GeV full energy injection. Accordingly, we investigated dependence of dynamic aperture on the betatron tune to obtain large dynamic apertures in the storage ring by a simulation method. We examined dynamic apertures by a tune survey within a specified tune space with and without machine errors. It is also shown how large are the dynamic apertures in the storage ring recovered are after the correction of a closed orbit distortion. The operating tune is examined from the viewpoint of dynamic apertures obtained by a tune survey.

0.3-nm SASE-FEL at PAL

Recent success in SASE-FEL experiments provides high confidence in achieving FEL radiation wavelengths as short as 0.1 nm.The SASE-XFEL requires multi-GeV electron beams with extremely low-emittance, short bunches, and long undulator systems. PAL is operating a 2.5-GeV electron linac as a full-energy injector to the PLS storage ring. With a proposed energy upgrade to 3.0 GeV and an in-vacuum undulator, PAL will be able to produce coherent X-ray radiation at wavelengths as short as 0.3 nm.This paper presents the preliminary design details for the proposed PAL-XFEL. The required undulator period is 12.5 mm with a 3-mm gap. The third harmonic enhancement technique can be used to obtain radiation wavelengths of 0.1 nm.The technical parameters related to these goals are reviewed.

The BEPCII project

Publisher Summary This chapter discusses Beijing Electron–Positron Collider spectrometer and its high statistical data samples for the Tau-Charm physics. BEPC runs at the threshold of the Charmonium family, the production cross sections are high, and the backgrounds are low. The high power klystrons of 45 MW will replace the existing 30MW klystrons to provide the full energy injection up to 1.89GeV. This is essential for the top-up injection to optimize the average luminosity of BEPCII. The design goals of the Beijing Spectrometer upgrade (BES III) are (1) to improve the detector resolution, specially the measurement of photon, and improve the particle identification to reduce the systematic errors, matching the high statistics of BEPCII, (2) to increase the acceptance of the detector; and (3) to adapt to the high event rate (3 KHz at the J/ψ peak) and the short bunch spacing (8 ns). Assuming BEPCII runs 5 months per year for physics, the average luminosity is 30% of peak luminosity, and the acceptance of 60–70%, each year, one could expect to obtain 6000 M–10000 M J/ψ events, or 2000 M ψ' events, or 10 M Tau pairs at 3.67GeV.