*2.1. Tandem Accelerator at WERC*

*2.1. Tandem Accelerator at WERC*  The tandem accelerator at WERC (Figure 2) accelerates negative ions which are injected from the two ion sources alternatively. One of the ion sources is a plasma sputter type source, and it generates hydrogen ions and heavy ions such as carbon ions. The typical peak intensity of pulsed negative hydrogen ions, which are used for the proton acceleration by the synchrotron, is 4 mA with a 20 Hz period and 25 μs duration*.* The other ion source is a kind of charge exchange type for the ionization of gas elements. Especially, the highly intense 4He negative ion beam, the current of which amounts to 40 μA, enables α The tandem accelerator at WERC (Figure 2) accelerates negative ions which are injected from the two ion sources alternatively. One of the ion sources is a plasma sputter type source, and it generates hydrogen ions and heavy ions such as carbon ions. The typical peak intensity of pulsed negative hydrogen ions, which are used for the proton acceleration by the synchrotron, is 4 mA with a 20 Hz period and 25 µs duration. The other ion source is a kind of charge exchange type for the ionization of gas elements. Especially, the highly intense <sup>4</sup>He negative ion beam, the current of which amounts to 40 µA, enables α particle irradiation with a high-density energy deposition into target materials.

particle irradiation with a high-density energy deposition into target materials. The acceleration voltage of the tandem accelerator amounts up to 5 MV. The high tension is generated by the Schenkel circuit with a 58-step voltage doubler rectifier, which rectifies 40 kHz RF power by a resonant transformer and an oscillator. The Schenkel rectifier, the acceleration tube, the high-tension terminal, and the resonant transformer are sustained by the insulation column support in the pressure tank. The pressure tank is filled with SF6 insulation gas at 0.6 MPa gauge. In order to enable the acceleration of the The acceleration voltage of the tandem accelerator amounts up to 5 MV. The high tension is generated by the Schenkel circuit with a 58-step voltage doubler rectifier, which rectifies 40 kHz RF power by a resonant transformer and an oscillator. The Schenkel rectifier, the acceleration tube, the high-tension terminal, and the resonant transformer are sustained by the insulation column support in the pressure tank. The pressure tank is filled with SF<sup>6</sup> insulation gas at 0.6 MPa gauge. In order to enable the acceleration of the highly intense beam from the ion sources, the conveyor current through the Schenkel rectifier amounts to 1 mA at the terminal high tension of 5 MV. The voltage ripple is 0.4 kVpp at the terminal high tension of 5 MV.

The charge exchange canal in the terminal has an inner diameter of 15 mm and a charge exchange effective length of about 1 m. Although the diameter of 15 mm seems to be large, the geometrical transmission efficiency is about 70% because of the large emittance of the negative ion from the ion sources. Argon gas for the charge exchange (stripper gas) is introduced into the middle of the canal. A differential pumping and the recirculation by four turbo-molecular pumps, each with a pumping speed of 50 L/s, enable the concentration of stripper gas in the canal with a large inner diameter. Such a stripper gas system realizes the 99% conversion of negative ions to positive at a gas thickness of 4 Pa·m. Additionally, the transmission efficiency along the following transport beam line to the synchrotron is achieved to be almost perfect. Therefore, a pulsed proton beam with peak intensity of 3 mA can be injected into the synchrotron. Table 1 summarizes the specifications of the tandem accelerator at WERC. be large, the geometrical transmission efficiency is about 70% because of the large emittance of the negative ion from the ion sources. Argon gas for the charge exchange (stripper gas) is introduced into the middle of the canal. A differential pumping and the recirculation by four turbo-molecular pumps, each with a pumping speed of 50 L/s, enable the concentration of stripper gas in the canal with a large inner diameter. Such a stripper gas system realizes the 99% conversion of negative ions to positive at a gas thickness of 4 Pa•m. Additionally, the transmission efficiency along the following transport beam line to the synchrotron is achieved to be almost perfect. Therefore, a pulsed proton beam with peak intensity of 3 mA can be injected into the synchrotron. Table 1 summarizes the specifications of the tandem accelerator at WERC.

highly intense beam from the ion sources, the conveyor current through the Schenkel rectifier amounts to 1 mA at the terminal high tension of 5 MV. The voltage ripple is 0.4 kVpp

The charge exchange canal in the terminal has an inner diameter of 15 mm and a charge exchange effective length of about 1 m. Although the diameter of 15 mm seems to

*Quantum Beam Sci.* **2021**, *5*, x FOR PEER REVIEW 3 of 18

at the terminal high tension of 5 MV.

**Figure 2***.* Tandem accelerator at WERC. **Figure 2.** Tandem accelerator at WERC.

**Table 1***.* Specifications of tandem accelerator. **Table 1.** Specifications of tandem accelerator.


*2.2. Synchrotron*

Injected ion ME (mass•energy value) 6 MeV•amu A proton beam with a maximum energy of 10 MeV is injected from the tandem accelerator into the synchrotron and is accelerated up to 200 MeV. Recently, for the proton acceleration, the injection energy has been set at 7 MeV.

by 4 TMP (50L/s/pump)

The overview of the synchrotron at WERC is shown in Figure 3. The circumference of the synchrotron is 33.2 m. The super periodicity is 4. Each lattice has a QF-BM-QD-BM permutation, and is operated in separated function style. Here, QF and QD are focusing and defocusing quadrupole magnets in the median plane, respectively, and BM means a bending magnet. Horizontal and vertical tunes are 1.75 and 0.85, respectively. A period of 2 s for the synchrotron acceleration consists of four modes of "injection and capture", "acceleration", "extraction", and "deceleration, then return to injection". The injection is performed in a multi-turn injection style. The RF knock out system slowly extracts the accelerated beam out of the separatrix in the horizontal phase space. The separatrix is generated by the excitation of sextupole magnets. By adjusting the RF strength by time, the variation in the intensity of the extracted beam by time is controlled to be reduced for eventby-event mode experiments such as a counter performance test and SEE investigations on semiconductor devices. The usual range of the beam intensity for the irradiation of space electronic devices is from 0.1 to 3 nA. Table 2 tabulates the principal specifications of the synchrotron at WERC. *Quantum Beam Sci.* **2021**, *5*, x FOR PEER REVIEW 5 of 18

**Figure 3***.* Synchrotron at WERC. **Figure 3.** Synchrotron at WERC.

the irradiation.

*2.3. Ion-Implanter* **Table 2.** Specifications of synchrotron.


currents available from the first and the second acceleration tubes are 50 and 30 mA, respectively. In the actual irradiation experiments, however, the beam current is reduced to less than several tens of micro A/cm2 to avoid beam heating of the target materials during


**Table 2.** *Cont*.
