2014 IMP & HIRFL Annual Report · 283 ·

6 - 29 Status Report of 320 kV High-voltage Platform in 2014

Li Jinyu, Liu Huiping, Kang Long and Zhang Tongmin

In 2014, the total operation time of 320 kV high-voltage platform for multi-discipline research with highly charged

ions was 5 500 h, including 3 200 h for experiments, 2 300 h for the machine preparation and commissioning due to

beam change and failure time. 46 experiments have been carried out, 28 of which were performed by the researchers

from other affiliations than the Institute of Modern Physics (IMP), 14 by those from IMP, and 4 attributed to

the commissioning for new ion species. 41% of operation time was contributed to IMP, 26% to other institutions,

24% to universities, 9% to enterprises (shown in Fig. 1). Among the research purpose, 69.7% of operation time was

for material research, 22% for atomic and molecular dynamics, 8.3% for plasma physics, nuclear astrophysics, and

molecular spectroscopy (represented in Fig. 2).

Fig. 1 (color online) Beam time distribution in terms ofaffiliation.

Fig. 2 (color online) Beam time distribution in terms ofresearch area.

The platform delivered ion beams for 17 kinds of isotopes, such as H, D, He, C, N, O, Ne, Ar, Kr, Xe, Bi, Fe, Li,

Au, Ag and so on, and the ion species amounts to 188. The energy of the ion beams ranged from 7 keV to 8 MeV,

corresponding to the extraction voltage from 7 to 300 kV. It was the first time for the platform to provide Li, Au,

and Ag ion beams, which were demanded by the researchers from Wuhan Institute of Physics and Mathematics,

University of Science and Technology Beijing and Shanghai Institute of Applied Physics, respectively.

Among these new ion species, the production of Li ions was the most challenging. Because pure Li is highly

reactive, we used LiF to produce Li ions instead of pure Li. 20 eµA of ion beam comprising Li2+ and N4+ was

obtained, and the exist of Li2+ was verified in the experiment. Ag and Au ion beams were also produced with oven.

25 eµA of Ag19+ and 7 eµA of Ag24+ were obtained at the RF power of 370 W, oven power of 28 W and oven

temperature of 800 ◦C. 10 eµA of Au24+ and 6 eµA of Au30+ were also obtained. The spectrums of Ag and Au ions

are plotted in Fig. 3 and Fig. 4.

Fig. 3 (color online) CSD of Ag ion beam. Fig. 4 (color online) CSD of Au ion beam.

Another experimental terminal has been designed and built at the platform for astrophysics. The assembly

precision, parameters of the magnetic components, and vacuum conditions have met the design requirements. Fig. 5

· 284 · IMP & HIRFL Annual Report 2014

Fig. 5 (color online) Experimental terminal for astrophysics.

is a photograph of the newly built experimental termi-

nal. The vacuum of 1.1×10−7 mbar was got at the

injection side, and 5.0×10−7 mbar at the extraction.

The beam transmission efficiency reached to 42%, which

needs improving further. The He2+ ion beam with the

energy of 400 keV was delivered to the terminal for the

first experiment.

Diverse experiments have been performed at the plat-

form in 2014, based on which there are about 80 SCI-

indexed, 15 ISTP-indexed papers published, and there

are another 5 papers published in key journals.

In summary, all the experiments whose beam-time

had been approved have been carried out successfullyin 2014. In addition, in order to enhance the performance of the platform, the injection component and sextupole

magnet of the ECR ion source, part of the control system, power sources, and high-temperature target chamber of

the material irradiation terminal have been upgraded. The platform will be tuned for more new ion species in the

future to meet the requirements of experiments.

6 - 30 Au Ion Production at 320 kV High Voltage Platform in 2014

Liu Huiping, Li Jinyu, Kang Long and Zhang Tongmin

Au ion beam was demanded at the 320 kV HV platform for multi-discipline research with highly charged ions

in 2014.

The oven technique was used to produce Au ions with 14.5 GHz ECR ion source at the 320 kV HV platform.

Oven technique is one of the popular methods for producing ions from a solid material at present. In many cases,

this technique is the most appropriate method to produce metal ion beams. It is simple in use and dose not cause

carbon contamination. However, the main problem relating to this method is the operation temperature.

In December 2014, we successfully produced Au ions from 14.5 GHz ECR ion source. Au powder, of 100 ∼200 µm in diameter, was load in the crucible of the micro-oven. When the micro-oven power, Pov, was 57.12 W,

Au ions appeared. With the increasing of Pov, the peaks of Au ions become higher. The typical beam intensity of

Au24+ was 8.10 eµA when Pov=76.14 W. Fig. 1 shows the screenshot of remote control. Microwave power, injection

pressure and extraction pressure were 330 W, 1.3×10−4 Pa, 2.8×10−5 Pa, respectively. The negative disc bias was

-40 V. Fig. 2 shows the charge state distribution of Au ions at two micro-oven power mentioned above. After 3 h,

the Au24+ output increased to 10.23 eµA without any adjustment. We can not get more intense ion beam of Au

for a long time due to the high melting point (1 377 K) and the operating temperature limitation of oven. Au24+

was supplied the accelerator for over 60 h.

Fig. 1 (color online) Screenshot of remote control. Fig. 2 Charge state distribution of Au ions. The ionsource was tuned to produce Au24+.

In the production of Au ions, O2 was used as the support gas and the extraction voltage was 15 kV. The gas

pressure, microwave power were adjusted to maximize the desired beam intensity.