REVIEW OF SCIENTIFIC INSTRUMENTS 85, 02A911 (2014)
The development of the high intensity electron cyclotron resonance ion source at China Institute of Atomic Energya) B. Tang,b) R. Ma, Y. Ma, L. Chen, Q. Huang, H. Liang, B. Cui, and W. Jiang China Institute of Atomic Energy, P.O. Box 275 (27), Beijing 102413, China
(Presented 11 September 2013; received 6 September 2013; accepted 6 October 2013; published online 30 October 2013) High-current microwave ion source has been under development over 15 years for accelerator driven sub-critical system research at China Institute of Atomic Energy, and the beam intensity higher than 140 mA proton beam is produced by this ion source with long lifetime and high reliability. The emittance of high intensity continue-wave and pulse beam is measured on a test-bench in the laboratory. Based on the good performance of this proton ion source, a new 120 mA deuterium ion source is proposed for a high intensity neutron generator. The ion source details and status will be presented. © 2013 AIP Publishing LLC. [http://dx.doi.org/10.1063/1.4826690] I. INTRODUCTION
High current electron cyclotron resonance (ECR) ion source has been under development over 15 years at China Institute of Atomic Energy (CIAE).1–3 The first ECR ion source at CIAE had been presented in Ref. 1. A 35 mA hydrogen beam was extracted from a 4 mm aperture of the source with about 550 W microwave power. The ion source has been developed for China Demonstration Prototype of Accelerator Driven Sub-critical System (CDPADS) project later, a 121 h long time test at 75 keV and 65 mA had been proceeded in 2004. The longest uninterrupted beam time is 110 h.2 In 2007, the ECR ion source and the low energy beam transport system (LEBT) had been interfaced to radio frequency quadruple (RFQ) developed by Institute of High Energy Physics (IHEP). After a very short period of test, the ion source and LEBT have been put into daily operation with good performance. The beam current before RFQ measured by a direct-current current transformer (DCCT) is 50 mA, and the current after RFQ is 46 mA. The beam transport efficiencies of LEBT and RFQ are 90% and 94%, respectively.3 In recent years, the lifetime and the reliability of the ion source have been improved to fulfill the high requirement of ADS.4 At present the source has the capacity of producing more than 140 mA hydrogen beam at 75 kV extracted routinely, and the RMS emittance measured is less than 0.2 π mm mrad. Three long time reliability tests operated at 75 keV and 100 mA extracted hydrogen current had been carried out on a test-bench. The total experimental time is over 400 h. In the last test, just 2 beam trips are recorded within the 220 h, and the total interrupted time is less than 40 s. The uninterrupted operation time is more than 150 h. Recently, another project named high intensified neutron generator (HINEG)5 promotes the further development of the high intensity ECR ion source (Fig. 1). HINEG is an accelerator-based D-T fusion neutron source with a DC line and a pulse line. Maximum neutron strength of 3 × 1013 n/s
will be generated by bombarding the target with a 100 mA beam of deuterons. A 120 mA deuterium beam at the energy of 65 keV will be generated from the ion source to fulfill this requirement. II. THE TEST-BENCH AND THE ION SOURCE
The experimental tests are carried out on a test-bench consisting of a microwave ion source, vacuum system, emittance measurement unit (EMU), mass separator, four-grid energy analyzer (FGA), beam stop, and control system. The setup is shown in Fig. 2. The vacuum chamber of the test bench is evacuated by three 1500 l/s turbo pumps. The vacuum pressure in the vacuum chamber is (2–5) × 10−3 Pa when the source is in operation. In addition, an emittance measurement unit and a four-grid energy analyzer are set in the first chamber to measure the emittance and the beam space-charge neutralization, respectively. A water cooled beam stop with a hole of 1 mm diameter in the center is equipped in the first chamber. The proton fraction is measured by a small magnetic mass separator and a Faraday-cup in the second chamber. The microwave power system is similar to the other ECR ion source. A 2 kW generator produces TE10-mode waves in a BJ-26 waveguide, followed by circulator/dummy load assembly to absorb the reflected power. It is followed by a 90◦ bend and an alumina microwave window for vacuum sealing.
a) Contributed paper, published as part of the Proceedings of the 15th
International Conference on Ion Sources, Chiba, Japan, September 2013. b) Electronic mail: [email protected]
0034-6748/2014/85(2)/02A911/3/$30.00
FIG. 1. Layout of HINEG. 85, 02A911-1
© 2013 AIP Publishing LLC
Tang et al.
Rev. Sci. Instrum. 85, 02A911 (2014)
Emittance measurement unit
160
Mass F-Cup separator
Slit Ion source
Beam stop Four-grid energy analyser
Chamber 2
Chamber 1
FIG. 2. The layout of the test-bench.
The microwave power is coupled into the cylindrical plasma chamber through a matching transformer waveguide. A stainless steel plasma chamber is used to overcome the problem of the etching of plasma chamber. No obvious etching on the plasma chamber wall or damage was observed after several hundred hours work. An electro-magnetic coil at 75 kV potential allows to vary the magnetic field of the electron resonance zones in the chamber and to optimize the ionization. The coil is surrounded by iron, which consists of the magnetic path together with ridge of the waveguide and the plasma electrode to make the source compact and lower the power consumption. A triple electrode system is used in this ion source. The magnetic field of this ECR ion source was optimized in recent years for the high current beam. The magnetic field on axis of the plasma chamber is shown in Fig. 3. The optimized field is much better than that of previous one.
Beam current[mA]
02A911-2
140 120 100 80 60
P=5E-3Pa
40
P=3.7E-3Pa
20
P=3E-3Pa
0 0.6
0.8
1
1.2
1.4
1.6
1.8
2
Microwave power[kW] FIG. 4. Beam intensity versus microwave power. The vacuum degree is measured in the first chamber.
proton fraction increases from 85% to 92% with increasing beam current. B. Emittance measurement
The emittance value of high intensity beam is difficult to get for the high beam power (>7.5 kW). The emittance of pulse beam is measured. An Allison scanner type6 emittance measurement unit is inserted into the first chamber to measure the emittance of the ion beam. The current for each position (x) and angle (x ) is the average peak value of several pulses, shown in Fig. 5. The experimental data show that the emittance of pulse beam is almost the same as that of CW beam, shown in Table I. The characterization of beam quality can be obtained by the emittance measurement of pulse beam. The vertical phase space emittance at 75 keV@120 mA is shown in Fig. 6. The frequency of the beam is 50 Hz and the duty factor is 5%.
III. THE EXPERIMENTAL RESULTS A. The beam current and the proton fraction
The ion beam current as a function of microwave power for different gas flow is shown in Fig. 4. The vacuum is measured in the first chamber. The ion current is sensitive to the amount of inlet gas. A maximum of 140 mA ion current can be extracted from a 6.5 mm aperture in diameter. The gas flow is about 5 sccm. The proton fraction is measured by a small magnetic mass separator and a Faraday-cup in the second chamber. The
0.12
C. Space-charge neutralization measurement
A FGA,7 which is a non-interceptive beam neutralization monitor, is being used to measure the beam neutralization property. The analyser has an entrance aperture of 8 mm in diameter. The total grid transparency is 64%. The FAG is mounted vertically located 36 cm from the ion source extraction electrode and the distance of the FGA entrance from the beam centerline is 10.5 cm, shown in Fig. 2. The data
unoptimised optimised
0.1 B [T]
0.08 0.06 0.04 0.02 0 0
10
20
30
40
50
60
Z [mm] FIG. 3. Magnetic field on axis of the plasma chamber. The plasma electrode is located at z = 0 and the bottom of the plasma chamber is at about z = 65 mm.
FIG. 5. The scheme of emittance measurement for the pulse beam.
02A911-3
Tang et al.
Rev. Sci. Instrum. 85, 02A911 (2014)
TABLE I. Experimental results of the emittance. Energy (keV) 60 60 75
Peak current (mA)
Cycle duty (%)
Frequency (Hz)
RMS emittance (π mm mrad)
41 41 120
100 20 5
CW 50 50
0.102 0.105 0.176
FIG. 8. The beam neutralization vs. hydrogen and nitrogen gas density in beam line. The beam current is 110 mA at the energy of 75 keV.
acquisition program was made using labview, with around 100 points on grid 3 voltages, each point averaged at least 100 times to eliminate the effect of noise. The experimental result is shown in Figs. 7 and 8. The degree of space-charge neutralization increases slowly from 98% to 99% with increasing beam current. And little variation of space-charge neutralization is observed with increasing of neutral gas density. The space-charge neutralization with nitrogen as neutral gas is better than that with hydrogen gas as neutral gas. IV. CONCLUSION FIG. 6. The emittance at 75 keV@120 mA .The frequency of beam is 50 Hz and the duty factor is 5%.
High intensity ECR ion sources have been under development at CIAE and the main characters had been measured. Based on the excellent performance of the ion source, a 120 mA deuterium ion source is being designed to fulfill the requirement of HINEG project. 1 B.
Cui, W. Jiang, and H. Sun, At. Energy Sci. Technol. 36(4), 201 (2002). B. Cui, R. Wang, Y. Ma, L. Li, C. Jiang, and W. Jiang, Rev. Sci. Instrum. 75(5), 1457 (2004). 3 Y. Ma, B. Cui, R. Ma, L. Li, C. Jiang, B. Tang, J. Deng, R. Wang, W. Jiang, J. Li, T. Huang, Y. Yao, and T. Xu, At. Energy Sci. Technol. 42(2), 209 (2008). 4 B. Cui, B. Tang, R. Ma, Q. Huang, Y. Ma, L. Chen, and W. Jiang, Rev. Sci. Instrum. 83(2), 02A321 (2012). 5 See http://www.fds.org.cn/newsshows.asp?newsid = 976 for the introduction of HINEG project. 6 P. W. Allison, J. D. Sherman, and D. B. Holtkamp, IEEE Trans. Nucl. Sci. 30, 2204 (1983). 7 J. Sherman, E. Pitcher, and P. Allison, in Proceedings of 1988 Linear Accelerator Conference, CEBAF Report 89-001 (Wukkuansburg, 1988), p. 155. 2
FIG. 7. The beam neutralization versus total beam current. The beam energy is 75 keV, and the gas density in the vacuum chamber is 2.66 × 1012 cm−3 .
Review of Scientific Instruments is copyrighted by the American Institute of Physics (AIP). Redistribution of journal material is subject to the AIP online journal license and/or AIP copyright. For more information, see http://ojps.aip.org/rsio/rsicr.jsp
The development of the high intensity electron cyclotron resonance ion source at China Institute of Atomic Energya) B. Tang,b) R. Ma, Y. Ma, L. Chen, Q. Huang, H. Liang, B. Cui, and W. Jiang China Institute of Atomic Energy, P.O. Box 275 (27), Beijing 102413, China
(Presented 11 September 2013; received 6 September 2013; accepted 6 October 2013; published online 30 October 2013) High-current microwave ion source has been under development over 15 years for accelerator driven sub-critical system research at China Institute of Atomic Energy, and the beam intensity higher than 140 mA proton beam is produced by this ion source with long lifetime and high reliability. The emittance of high intensity continue-wave and pulse beam is measured on a test-bench in the laboratory. Based on the good performance of this proton ion source, a new 120 mA deuterium ion source is proposed for a high intensity neutron generator. The ion source details and status will be presented. © 2013 AIP Publishing LLC. [http://dx.doi.org/10.1063/1.4826690] I. INTRODUCTION
High current electron cyclotron resonance (ECR) ion source has been under development over 15 years at China Institute of Atomic Energy (CIAE).1–3 The first ECR ion source at CIAE had been presented in Ref. 1. A 35 mA hydrogen beam was extracted from a 4 mm aperture of the source with about 550 W microwave power. The ion source has been developed for China Demonstration Prototype of Accelerator Driven Sub-critical System (CDPADS) project later, a 121 h long time test at 75 keV and 65 mA had been proceeded in 2004. The longest uninterrupted beam time is 110 h.2 In 2007, the ECR ion source and the low energy beam transport system (LEBT) had been interfaced to radio frequency quadruple (RFQ) developed by Institute of High Energy Physics (IHEP). After a very short period of test, the ion source and LEBT have been put into daily operation with good performance. The beam current before RFQ measured by a direct-current current transformer (DCCT) is 50 mA, and the current after RFQ is 46 mA. The beam transport efficiencies of LEBT and RFQ are 90% and 94%, respectively.3 In recent years, the lifetime and the reliability of the ion source have been improved to fulfill the high requirement of ADS.4 At present the source has the capacity of producing more than 140 mA hydrogen beam at 75 kV extracted routinely, and the RMS emittance measured is less than 0.2 π mm mrad. Three long time reliability tests operated at 75 keV and 100 mA extracted hydrogen current had been carried out on a test-bench. The total experimental time is over 400 h. In the last test, just 2 beam trips are recorded within the 220 h, and the total interrupted time is less than 40 s. The uninterrupted operation time is more than 150 h. Recently, another project named high intensified neutron generator (HINEG)5 promotes the further development of the high intensity ECR ion source (Fig. 1). HINEG is an accelerator-based D-T fusion neutron source with a DC line and a pulse line. Maximum neutron strength of 3 × 1013 n/s
will be generated by bombarding the target with a 100 mA beam of deuterons. A 120 mA deuterium beam at the energy of 65 keV will be generated from the ion source to fulfill this requirement. II. THE TEST-BENCH AND THE ION SOURCE
The experimental tests are carried out on a test-bench consisting of a microwave ion source, vacuum system, emittance measurement unit (EMU), mass separator, four-grid energy analyzer (FGA), beam stop, and control system. The setup is shown in Fig. 2. The vacuum chamber of the test bench is evacuated by three 1500 l/s turbo pumps. The vacuum pressure in the vacuum chamber is (2–5) × 10−3 Pa when the source is in operation. In addition, an emittance measurement unit and a four-grid energy analyzer are set in the first chamber to measure the emittance and the beam space-charge neutralization, respectively. A water cooled beam stop with a hole of 1 mm diameter in the center is equipped in the first chamber. The proton fraction is measured by a small magnetic mass separator and a Faraday-cup in the second chamber. The microwave power system is similar to the other ECR ion source. A 2 kW generator produces TE10-mode waves in a BJ-26 waveguide, followed by circulator/dummy load assembly to absorb the reflected power. It is followed by a 90◦ bend and an alumina microwave window for vacuum sealing.
a) Contributed paper, published as part of the Proceedings of the 15th
International Conference on Ion Sources, Chiba, Japan, September 2013. b) Electronic mail: [email protected]
0034-6748/2014/85(2)/02A911/3/$30.00
FIG. 1. Layout of HINEG. 85, 02A911-1
© 2013 AIP Publishing LLC
Tang et al.
Rev. Sci. Instrum. 85, 02A911 (2014)
Emittance measurement unit
160
Mass F-Cup separator
Slit Ion source
Beam stop Four-grid energy analyser
Chamber 2
Chamber 1
FIG. 2. The layout of the test-bench.
The microwave power is coupled into the cylindrical plasma chamber through a matching transformer waveguide. A stainless steel plasma chamber is used to overcome the problem of the etching of plasma chamber. No obvious etching on the plasma chamber wall or damage was observed after several hundred hours work. An electro-magnetic coil at 75 kV potential allows to vary the magnetic field of the electron resonance zones in the chamber and to optimize the ionization. The coil is surrounded by iron, which consists of the magnetic path together with ridge of the waveguide and the plasma electrode to make the source compact and lower the power consumption. A triple electrode system is used in this ion source. The magnetic field of this ECR ion source was optimized in recent years for the high current beam. The magnetic field on axis of the plasma chamber is shown in Fig. 3. The optimized field is much better than that of previous one.
Beam current[mA]
02A911-2
140 120 100 80 60
P=5E-3Pa
40
P=3.7E-3Pa
20
P=3E-3Pa
0 0.6
0.8
1
1.2
1.4
1.6
1.8
2
Microwave power[kW] FIG. 4. Beam intensity versus microwave power. The vacuum degree is measured in the first chamber.
proton fraction increases from 85% to 92% with increasing beam current. B. Emittance measurement
The emittance value of high intensity beam is difficult to get for the high beam power (>7.5 kW). The emittance of pulse beam is measured. An Allison scanner type6 emittance measurement unit is inserted into the first chamber to measure the emittance of the ion beam. The current for each position (x) and angle (x ) is the average peak value of several pulses, shown in Fig. 5. The experimental data show that the emittance of pulse beam is almost the same as that of CW beam, shown in Table I. The characterization of beam quality can be obtained by the emittance measurement of pulse beam. The vertical phase space emittance at 75 keV@120 mA is shown in Fig. 6. The frequency of the beam is 50 Hz and the duty factor is 5%.
III. THE EXPERIMENTAL RESULTS A. The beam current and the proton fraction
The ion beam current as a function of microwave power for different gas flow is shown in Fig. 4. The vacuum is measured in the first chamber. The ion current is sensitive to the amount of inlet gas. A maximum of 140 mA ion current can be extracted from a 6.5 mm aperture in diameter. The gas flow is about 5 sccm. The proton fraction is measured by a small magnetic mass separator and a Faraday-cup in the second chamber. The
0.12
C. Space-charge neutralization measurement
A FGA,7 which is a non-interceptive beam neutralization monitor, is being used to measure the beam neutralization property. The analyser has an entrance aperture of 8 mm in diameter. The total grid transparency is 64%. The FAG is mounted vertically located 36 cm from the ion source extraction electrode and the distance of the FGA entrance from the beam centerline is 10.5 cm, shown in Fig. 2. The data
unoptimised optimised
0.1 B [T]
0.08 0.06 0.04 0.02 0 0
10
20
30
40
50
60
Z [mm] FIG. 3. Magnetic field on axis of the plasma chamber. The plasma electrode is located at z = 0 and the bottom of the plasma chamber is at about z = 65 mm.
FIG. 5. The scheme of emittance measurement for the pulse beam.
02A911-3
Tang et al.
Rev. Sci. Instrum. 85, 02A911 (2014)
TABLE I. Experimental results of the emittance. Energy (keV) 60 60 75
Peak current (mA)
Cycle duty (%)
Frequency (Hz)
RMS emittance (π mm mrad)
41 41 120
100 20 5
CW 50 50
0.102 0.105 0.176
FIG. 8. The beam neutralization vs. hydrogen and nitrogen gas density in beam line. The beam current is 110 mA at the energy of 75 keV.
acquisition program was made using labview, with around 100 points on grid 3 voltages, each point averaged at least 100 times to eliminate the effect of noise. The experimental result is shown in Figs. 7 and 8. The degree of space-charge neutralization increases slowly from 98% to 99% with increasing beam current. And little variation of space-charge neutralization is observed with increasing of neutral gas density. The space-charge neutralization with nitrogen as neutral gas is better than that with hydrogen gas as neutral gas. IV. CONCLUSION FIG. 6. The emittance at 75 keV@120 mA .The frequency of beam is 50 Hz and the duty factor is 5%.
High intensity ECR ion sources have been under development at CIAE and the main characters had been measured. Based on the excellent performance of the ion source, a 120 mA deuterium ion source is being designed to fulfill the requirement of HINEG project. 1 B.
Cui, W. Jiang, and H. Sun, At. Energy Sci. Technol. 36(4), 201 (2002). B. Cui, R. Wang, Y. Ma, L. Li, C. Jiang, and W. Jiang, Rev. Sci. Instrum. 75(5), 1457 (2004). 3 Y. Ma, B. Cui, R. Ma, L. Li, C. Jiang, B. Tang, J. Deng, R. Wang, W. Jiang, J. Li, T. Huang, Y. Yao, and T. Xu, At. Energy Sci. Technol. 42(2), 209 (2008). 4 B. Cui, B. Tang, R. Ma, Q. Huang, Y. Ma, L. Chen, and W. Jiang, Rev. Sci. Instrum. 83(2), 02A321 (2012). 5 See http://www.fds.org.cn/newsshows.asp?newsid = 976 for the introduction of HINEG project. 6 P. W. Allison, J. D. Sherman, and D. B. Holtkamp, IEEE Trans. Nucl. Sci. 30, 2204 (1983). 7 J. Sherman, E. Pitcher, and P. Allison, in Proceedings of 1988 Linear Accelerator Conference, CEBAF Report 89-001 (Wukkuansburg, 1988), p. 155. 2
FIG. 7. The beam neutralization versus total beam current. The beam energy is 75 keV, and the gas density in the vacuum chamber is 2.66 × 1012 cm−3 .
Review of Scientific Instruments is copyrighted by the American Institute of Physics (AIP). Redistribution of journal material is subject to the AIP online journal license and/or AIP copyright. For more information, see http://ojps.aip.org/rsio/rsicr.jsp
