Jinxiang Yu

Study on proton fraction of beams extracted from electron cyclotron resonance ion source.

A permanent magnet electron cyclotron resonance ion source PMECR II is used to generate proton ions for radio frequency quadrupole (RFQ) injection at Peking University (PKU). The proton fractions of the extracted beam were measured at the positions both after extraction system of ion source and the end of low energy beam transport line (LEBT). Experiments show that the proton fraction has a rise time within a beam pulse, and its value varies with pulse width and microwave power. The proton fractions measured at different positions are comparable.

The deuteron injector progress of the Peking University Neutron Imaging Facility project.

A deuteron radio frequency quadrupoles injector h has been developed at Peking University. A permanent magnetic electron cyclotron resonance (ECR) ion source is used in the injector system. A 50 keV 100 mA proton beam has been extracted from the ECR ion source and the measured normalized rms emittance is 0.11-0.14pi mm mrad. A deuteron beam has also been extracted at 50 kV with 83 mA total current and its emittance is less than 0.18pi mm mrad. The proton beam transmission has been investigated on a low energy beam transport test bench, and up to 93% transmission can be reached. The new injector with two solenoids has been designed and is being constructed. All the development results will be presented in this paper.

Minipermanent magnet high-current microwave ion source

A 2.45GHz high-current microwave ion source with permanent magnet was developed at Peking University. The source body is about 10cm in diameter and 10cm in height, and its weight is less than 5kg. It can operate in both pulse and continuous wave (cw) modes. In pulse mode, more than 100mA hydrogen ion current was extracted from a 5mm ion extraction aperture, when the microwave power is 500W and the extraction voltage is 45kV, which corresponds to a beam density of 500mA∕cm2. In cw mode, up to 60mA of hydrogen ion current can be extracted, and the beam density is 300mA∕cm2 at the same conditions. The proton ratio is about 80% and the normalized root-mean-square emittance is less than 0.1πmmmrad in both modes.

Deuteron injector for Peking University Neutron Imaging Facility project.

The deuteron injector developed for the PKUNIFTY (Peking University Neutron Imaging Facility) has been installed and commissioned at Peking University (PKU). The injector system must transfer 50 keV 50 mA of D(+) ion beam to the entrance of the 2 MeV radio frequency quadrupole (RFQ) with 10% duty factor (1 ms, 100 Hz). A compact 2.45 GHz permanent magnet electron cyclotron resonance (PMECR) ion source and a 1.36 m long low energy beam transport (LEBT) line using two solenoids was developed as the deuteron injector. A φ5 mm four-quadrant diaphragm was used to simulate the entrance of RFQ electrodes. The beam parameters are measured after this core with an emittance measurement unit (EMU) and a bending magnet for ion fraction analysis at the end of injector. During the commissioning, 77 mA of total deuteron beam was extracted from PMECR and 56 mA of pure D(+) beam that passed through the φ5 mm four-quadrant diaphragm was obtained at the position of RFQ entrance with the measured normalized rms emittance 0.12-0.16π mm mrad. Ion species analysis results show that the deuteron fraction is as high as 99.5%. All of the parameters satisfy PKUNIFTYs requirements. In this paper, we will describe the deuteron injector design and report the commissioning results as well as the initial operation.

Preliminary studies on space charge compensation by analyzing residual argon gas ion signals

An experimental method is related to research the space charge compensation (SCC) effect in low energy intense proton beams by analyzing residual gas (RG) ion signals. The signal curves were measured with an energy spectrometer under the RG pressure from 1.2x10(-3) to 1.6x10(-2) Pa. Most of the data showed a similar trend with our theoretical predicts. From the RG ion energy spectra the potential distribution in the beam was calculated both with and without the SCC effect. Moreover, as a preliminary result, a best compensating point is achieved for the low energy beam transport transmission of 40 KeV, 60 mA H(+) beam in Peking University.

Upgrade of the extraction system of permanent magnet electron cyclotron resonance ion source

A set of new ion extraction electrodes have been designed for the permanent magnetic electron cyclotron resonance ion source at Peking University to improve beam quality and transmission. PBGUNS has been used to optimize the extraction electrodes and simulate the beam behavior at the extraction region. The experiments showed that with the new system, the beam half divergence angle can be less than 40 mrad and the normalized rms emittance is about 0.13pi mm mrad when the extracted current is 100 mA at 50 keV in pulse mode. The voltage of the suppression electrode has great effect on beam divergence. The effect of the microwave power and gas flow is also studied.

Small microwave ion source for an ion implanter

Three kinds of small 24.5 GHz microwave ion sources have been developed for a middle current implanter. The magnetic fields of the sources are produced by an electromagnetic coil, electromagnetic coil added permanent magnet ring, and permanent magnet rings, respectively. Adopting single‐hole accel–decel extraction electrodes with about 5 mA of nitrogen and oxygen, ion current can be extracted from them. The microwave power consumption is about 100–200 W.

Experimental results of an electron cyclotron resonance oxygen source and a low energy beam transport system for 1 MeV integral split ring radio frequency quadruple accelerator upgrade project.

To meet the requirements of developing separated function radio frequency quadruple (rfq) and upgrading the 1 MeV integral split ring rfq accelerator, an electron cyclotron resonance O(+) ion source and low energy beam transport (LEBT) system have been developed. Using two Einzel lenses to focus the beam, more than 6 mA O(+) peak beam current with energy of 22 keV can be easily obtained at the end of LEBT when the duty faction is at 1/6. The normalized root-mean-square emittance of 90% of the beam is about 0.12pi mm mrad. By changing the focusing power of lenses, the beam waist can be shifted from 80 mm before the beam diaphragm 2 to 80 mm after it. The experimental results will be presented in this article.

A simple ferromagnetic circuit for a solenoid lens

Several studies have been carried out to explore a simple ferromagnetic circuit to obtain a more intense field inside a solenoid lens. Model experimental results show that, under the circumstance that the ferromagnetic circuit is not saturated and the current remains constant, a more intense magnetic field can be obtained using the semi-enclosed ferromagnetic circuit developed in this paper. The semi-closed solenoid lens is simple, economical and easy to cool and maintain. A semi-enclosed solenoid lens has been manufactured for transporting 50 keV, 50 mA H+ beams at Peking University (PKU).

A Side Extraction PIG Ion Source with Permanent Magnetic Mirror Field

The present work describes the principle, structure and experimental results of a side extraction PIG ion source with permanent magnetic mirror type field. The source is light and handy with low power consumption and high ionization efficiency. In the experiments using BF3, N2 and Ar, total beam current of 1-2 ma can be obtained with 50-150 watt arc power. The relative yields of 11B+, 14N+, 40Ar2+, 11B2+ and 14N2+ are 50-60%, 70-80%, 20-30%, 5% and 7% that of total beam, respectively. 11B3+, 14N5+ and 40Ar6+ are also measurable. In addition, a multicathode side extraction PIG ion source has been developed, in which a new extracting way called ACE (anode-cathode-extraction electrode) are used.