The HEPS plans to adopt on-axis injection scheme because the dynamic aperture of machine is not large enough for off-axis injection for its baseline 7BA lattice design. A couple sets of strip-line kicker and fast pulser of ± 15 kV amplitude, 15 ns pulse bottom width are needed for bunch spacing of 10 ns to minimize perturbation on adjacent bunches. To achieve these requirement, a multifaceted R&D program including the strip-line kicker and HV pulser, was initiated last 2 years. So far, the prototype development of a 750 mm long strip-line kicker and a DSRD pulser was completed and the preliminary test results show they can meet the baseline requirement of the HEPS.

Strip-line kicker and fast pulser R&D for the HEPS on-axis injection system

Abstract Purpose The physics design of the High Energy Photon Source (HEPS) was finished after many times of iteration. Hereby, the typical equilibrium electron beam parameters corresponding to the proposed two baseline operation modes in the baseline design of HEPS are presented. Methods To compute the equilibrium parameters of the electron beam, the lattice parameters, RF parameters, and the parameters of the insertion devices (IDs) were determined first. Furthermore, it is more precise to use the full-current electron beam parameters in the estimations of the performance of the synchrotron light. Therefore, not only the single-particle dynamics but also the current-dependent collective effects need to be considered in the computations of the full-current, equilibrium parameters of the electron beam. Both analytic computations and multi-particle tracking simulations were carried out. Results The full-current, equilibrium parameters of the electron beams in the HEPS storage ring are presented in this paper. Moreover, the main beam parameters in the injector (the booster and the LINAC), corresponding to the two baseline operation modes of the storage ring, are also presented. Conclusion The typical electron beam parameters corresponding to the two baseline operation modes are given in detail in this paper. 

/pdf/equilibrium-electron-beam-parameters-of-the-high-energy-25vvoubv.pdf

Equilibrium electron beam parameters of the High Energy Photon Source

In order to make BEPC-II to run at a higher energy, the Institute of High Energy Physics undertook an upgrading project. One of the important factors limiting the energy boost is the power and performance of the dipole magnet power supplies; therefore, these four magnet power supplies are developed for the BEPC-II upgrading. The power supplies adopt topologies of thyristor rectifiers to realize a high-power output. In the control unit of each power supply, a digital current closed loop is adopted, and the key components in the feedback loop are thermostatically controlled. In order to improve the performances of the power supplies, analog voltage regulators are added to the inner control loops. These four power supplies have been tested and have already been officially used in BEPC-II, and their powers have reached the requirements of the upgrading. The test results of the current stability are described and shown in this paper, which testifies that the stabilities meet the design parameters. A digital control is applied to each SCR rectifier control. The performances of the power supplies are improved by the combination of digital current control loops and the analog voltage control loops, which makes the performances of the dipole magnet power supplies meet the requirements of the upgrading project.

Development of dipole magnet power supply for BEPC-II energy upgrading project

Stripline kickers are commonly used for on-axis injection in the low emittance rings. The beam coupling impedances of the kickers normally show large contributions to the total impedance budget. In the High Energy Photon Source, the necessity of the short pulse bottom width (less than 10 ns) and strong deflection field requires the kicker to have a short length and a small gap between the electrodes, respectively. A new five-cell stripline kicker is proposed in order to save longitudinal space as well as to reduce the beam coupling impedance. Comprehensive studies have been undertaken to characterize the impedance of the stripline kicker. The beam coupling impedance and heat load dissipation on the kicker due to the beam passage are studied numerically. Strategies to further reduce the impedance are discussed. In addition, impedance bench measurements are launched to identify the impedance of the kicker experimentally. The longitudinal beam coupling impedance is measured with different terminations by using coaxial wire method. A satisfactory agreement has been reached between the numerical predictions and the measurements. A novel fasten block design with ceramic is proposed for the wire stretching and the center holding of the inner conductor in a small beam pipe.

https://link.aps.org/pdf/10.1103/PhysRevAccelBeams.24.034401

Impedance optimization and measurements of the injection stripline kicker

In this paper, a simulation model of p type PiN high voltage pulse open switch is established. The switch operates in “punch through” mode, with a 4 kA/cm2 cut-off current density and sub-nanosecon...

Study on cut-off characteristics of sub-nanosecond silicon carbide PiN switch

Verification of bottom measurement method based on 3D laser scanner

Background: Administrative data permits analysis of large cohorts but relies on International Classification of Diseases, Ninth and Tenth Revision, Clinical Modification (ICD) codes that may not reflect true congenital heart defects (CHD). Methods: 1497 cases with at least one encounter between 1/1/2010 -- 12/31/2019 in two healthcare systems (one adult, one pediatric) identified by at least one of 87 ICD CHD codes were validated through chart review for the presence of CHD and CHD anatomic group. Results: Inter- and intra-observer reliability averaged > 95%. Positive predictive value (PPV) of ICD codes for CHD was 68.1% (1020/1497) overall, 94.6% (123/130) for cases identified in both healthcare systems, 95.8% (249/260) for severe codes, 52.6% (370/703) for shunt codes, 75.9% (243/320) for valve codes, 73.5% (119/162) for shunt and valve codes, and 75.0% (39/52) for "Other CHD" (7 ICD codes). PPV for cases with >1 unique CHD code was 85.4% (503/589) vs. 56.3% (498/884) for one CHD code. Of cases with secundum atrial septal defect ICD codes 745.5/Q21.1 in isolation, 30.9% (123/398) had a confirmed CHD. Patent foramen ovale was present in 66.2% (316/477) of false positives (FP). The median number of unique CHD-coded encounters was higher for true positives (TP) than FP (2.0; interquartile range [IQR]: 1.0-3.0 vs 1.0; IQR:1.0-1.0, respectively, p<0.0001). TP had younger mean age at first encounter with a CHD code than FP (22.4 years vs 26.3 years, p=0.0017). Conclusion: PPV of CHD ICD codes varies by characteristics for detection of CHD by ICD code and anatomic grouping. While an ICD code for severe CHD and/or the presence of a case in more than one data source, regardless of anatomic group, is associated with higher PPV for CHD, most TP cases did not have these characteristics. The development of algorithms to improve accuracy may improve administrative data for CHD surveillance.

/pdf/international-classification-of-diseases-icd-codes-for-24hkbz0q.pdf

International Classification of Diseases (ICD) Codes for Congenital Heart Defects (CHD) Have Variable and Limited Accuracy for Detecting CHD Cases

The superfast kickers are required for the HEPS storage ring on-axis injection system due to its very small dynamic aperture. A 750-mm-long stripline pair type of kicker prototype was researched and developed to demonstrate achieved performance of bandwidth, impedance, kicker strength, field uniformity and beam power loss.
 The cross sections of the kicker main body and the end of taper part are optimized for a good impedance matching and field uniformity. 3D simulation further optimizes the taper part to minimize the beam power loss and maintain a lower reflection. The high-voltage feedthrough is also designed and optimized by 3D CST. RF and high-voltage measurements are taken to verify the design of kicker assembly.
 The testing transmission odd-mode impedance is 50 ± 0.5 Ω, the even-mode impedance is 60 ± 0.5 Ω, and return loss is less than − 13 dB. The peak voltage and the rise time of pulse width inserting kicker assembly just decrease 3% of 20 kV and slow down 80 ps, respectively. RF testing results agree well with the simulation ones, which meet the design specification. The kicker assembly works well at ± 20 kV pulse.

Development of a 750-mm-long stripline kicker for HEPS

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