*3.1. Beamline of the Synchrotron in Irradiation Room 4*

In irradiation room 4, we can perform irradiation experiments with ion beams extracted from the synchrotron. Figure 5 shows the layout of the beam line in irradiation room 4. After an ion beam is accelerated by the synchrotron and transported to irradiation room 4, the beam is deflected to the direction of the target samples by a bending magnet and is shaped by two sets of quadrupole magnet doublets. Then, the ion beam is emitted into the atmosphere through a copperized polyimide thin film window. In order to form the appropriate irradiation field on the target surface, the ion beam is wobbled by a set of wobbling magnets and/or scattered by a tungsten scatterer and collimated by a brass block collimator. *Quantum Beam Sci.* **2021**, *5*, x FOR PEER REVIEW 7 of 18

**Figure 5.** Beam line in irradiation room 4. **Figure 5.** Beam line in irradiation room 4.

The intensity distribution of the cross section of the primary proton beam at 200 MeV kinetic energy has almost an axially symmetrical Gaussian shape with around 1.5 cm standard deviation about beam direction. We call this beam as "pencil beam". The usual irradiation area on the sample is within 2 cm by 2 cm squares; therefore, the pencil beam covers the irradiation area with a flatness (the ratio of intensity at the edge of the irradiation area to that at the center) of more than 80%. Sometimes, much more severe uniformity is required to the intensity distribution. In such case, we use a tungsten scatterer with a thickness of 0.1 mm to make a flatness of more than 94%. The intensity distribution of the cross section of the primary proton beam at 200 MeV kinetic energy has almost an axially symmetrical Gaussian shape with around 1.5 cm standard deviation about beam direction. We call this beam as "pencil beam". The usual irradiation area on the sample is within 2 cm by 2 cm squares; therefore, the pencil beam covers the irradiation area with a flatness (the ratio of intensity at the edge of the irradiation area to that at the center) of more than 80%. Sometimes, much more severe uniformity is required to the intensity distribution. In such case, we use a tungsten scatterer with a thickness of 0.1 mm to make a flatness of more than 94%.

In TID experiments, the beam intensity amounts to around 3 nA, which corresponds to a flux of 2.5 × 108 cm–2s–1 in the case of an irradiation area of 2 cm by 2 cm squares and a scatterer thickness of 0.1 mm. In experiments for the single event effect (SEE), the ion beam flux is required to be reduced to less than 1 × 107 cm−2s−1. Thus, the beam intensity is reduced to 0.1 nA by adjusting the strength of the RF kicker. In order to obtain a beam flux of less than 1 × 106 cm−2s−1, a thicker scatterer is used for the reduction in the area

The proton beam can be spread to large targets, such as a 10 cm by 10 cm square for instance. SEE experiments with a flux of less than 106 cm–2s–1 can be performed by using only the scatterer to form a large irradiation field. In the case of 107 cm–2s–1 flux experiment, the beam is wobbled by a set of wobbling magnets to improve the beam utilization effi-

In several SEE experiments, the cross section for the SEE occurrence is measured as a function of the linear energy transfer (LET) of primary beam in the target material. In order to perform the experiment, the energy of the projectile has to be changed for each LET value. Although the beam energy from the synchrotron is variable, the excitation pattern of all magnets and acceleration RF, and beam transport setup have to be changed for each beam energy. Therefore, an energy degrader is used instead of a conventional method for the variation of the beam energy. The degrader, made of resin which is waterequivalent in the proton energy loss, can change its thickness in units of 1 mm from 2 to 270 mm. The degrader is set at a position immediate upstream of the irradiation target. An ionization chamber (shown as "dose monitor" in Figure 5) is used for the dose control. As the ionization efficiency relates to a function of the energy deposition by passing particles, the dose measured by the ionization chamber is calibrated for each energy variation by measuring the beam current at the beam dump. The probability of the recombination of ion-electron pairs is a function of density of the pairs produced in the ionization chamber. Therefore, the calibration of the dose monitor is also performed for each variation of beam intensity and irradiation area by the comparison between the averaged current signals from the dose monitor and beam dump for 3~5 times measurements. The

density of the beam.

ciency.

In TID experiments, the beam intensity amounts to around 3 nA, which corresponds to a flux of 2.5 <sup>×</sup> <sup>10</sup><sup>8</sup> cm−<sup>2</sup> s −1 in the case of an irradiation area of 2 cm by 2 cm squares and a scatterer thickness of 0.1 mm. In experiments for the single event effect (SEE), the ion beam flux is required to be reduced to less than 1 <sup>×</sup> <sup>10</sup><sup>7</sup> cm−<sup>2</sup> s −1 . Thus, the beam intensity is reduced to 0.1 nA by adjusting the strength of the RF kicker. In order to obtain a beam flux of less than 1 <sup>×</sup> <sup>10</sup><sup>6</sup> cm−<sup>2</sup> s −1 , a thicker scatterer is used for the reduction in the area density of the beam.

The proton beam can be spread to large targets, such as a 10 cm by 10 cm square for instance. SEE experiments with a flux of less than 10<sup>6</sup> cm−<sup>2</sup> s −1 can be performed by using only the scatterer to form a large irradiation field. In the case of 10<sup>7</sup> cm−<sup>2</sup> s −1 flux experiment, the beam is wobbled by a set of wobbling magnets to improve the beam utilization efficiency.

In several SEE experiments, the cross section for the SEE occurrence is measured as a function of the linear energy transfer (LET) of primary beam in the target material. In order to perform the experiment, the energy of the projectile has to be changed for each LET value. Although the beam energy from the synchrotron is variable, the excitation pattern of all magnets and acceleration RF, and beam transport setup have to be changed for each beam energy. Therefore, an energy degrader is used instead of a conventional method for the variation of the beam energy. The degrader, made of resin which is water-equivalent in the proton energy loss, can change its thickness in units of 1 mm from 2 to 270 mm. The degrader is set at a position immediate upstream of the irradiation target.

An ionization chamber (shown as "dose monitor" in Figure 5) is used for the dose control. As the ionization efficiency relates to a function of the energy deposition by passing particles, the dose measured by the ionization chamber is calibrated for each energy variation by measuring the beam current at the beam dump. The probability of the recombination of ion-electron pairs is a function of density of the pairs produced in the ionization chamber. Therefore, the calibration of the dose monitor is also performed for each variation of beam intensity and irradiation area by the comparison between the averaged current signals from the dose monitor and beam dump for 3~5 times measurements. The doses are controlled with an error (standard deviation) of almost 2% and 1% for the 100 MeV proton irradiation to the area of 10 cm by 10 cm with flux of 3 <sup>×</sup> <sup>10</sup><sup>6</sup> and <sup>1</sup> <sup>×</sup> <sup>10</sup><sup>7</sup> cm−<sup>2</sup> s −1 , respectively.

The synchrotron beam is used to measure the radiation effects not only on space electronics but also on radiation detectors to be used in space for astronomical phenomena. As usual detectors count each particle and/or gamma/X-ray, the charged particle energy and flux under the circumstances around the space probe have to be simulated. In these experiments, the beam intensity is reduced to less than 10 kHz. The intensity is controlled by the charged particle counting using a counter-telescope with two sets of plastic scintillators read by photomultiplier tubes.
