06aB13
Nd:YAG トムソン散乱計測装置に最適なデータ処理システムによる測定精度の改善
Improvement of measurement accuracy by optimum data acquisition
system for Nd:YAG Thomson scattering system
南貴司 1 、山田一博 2 、舟場久芳 2 、伊藤康彦 2 、中西秀哉 2 、波多江仰紀 3
1Takashi MINAMI, 2 Ichihiro YAMADA, 2 Hisamichi FUNABA, 2 Yasuhiko ITOH,
2Hideya NAKANISHI, 3 Takaki HATAE
京都大学エネルギー理工学研究所 1 、核融合科学研究所 2 、日本原子力研究開発機構 3 、1IAE Kyoto Univ., 2 NIFS, 3 JAEA
Precise time evolution information of plasma proﬁles is indispensable to improve a plasma performance.
An Nd:YAG Thomson scattering method has advantages for the proﬁle measurement, because it can measure local values of plasma electron density and temperature, in addition, it provides a precise time evolutionof the plasma proﬁle due to the high repetition rate of the Nd:YAG laser. However, the Nd:YAG Thomson measurement requires higher speed data processing, because the short laser pulse width ( ∼ 10ns ) is
required for improvement of S/N ratio. Therefore, we have developed a new high speed analog to digitalconvertor for data processing of the Nd:YAG Thomson scattering measurement ( High speed YAG Thomson scattering AD Convertor: HYADC ). Until now, a charge integrating type AD convertor was mainly
utilized for the Nd:YAG Thomson scattering, because there has been no high speed and high resolution
AD converter chip. Recently, the high speed AD converter of 12 bits resolution and 500MHz sample rate
( AD5463, Texas Instruments inc. ) is developed, then we are developing the HYADC that can directly
convert the scattered light signal to the digital signal. The direct conversion method of the HYADC has
several advantages as follows.
1. An increased number of the sampled data compared to the charge integrating type AD convertor
improve a signal to noise ratio by over 10 times.
2. A precise background light reduction can be performed using the digitized data of which signal isdetected just after a laser injection.
3. The HYADC can analyze a short pulse interval laser injection of the multi-pulse Nd:YAG Thomson
scattering measurement. Even if the signal is overlapped, The HYADC can separate both signals.
The HYADC has a ring buﬀer memory and a stop trigger due to sampling only a short period in which
the scattered light is detected. Consequently, an amount of the total data that is stored in data storages
is reduced to below 0.01% compared to a full data conversion. The data transfer to the analysis computeris executed by SiTCP[1] which has developed by KEK. The SiTCP can transfer the data by the TCP
protocol using a wire logic circuit without CPU. Then the real time data acquisitions are realized, whichis required for a real time feedback plasma control of the fusion plasma. Because the AD converter control
unit, the data memory unit, and the data transfer unit are consolidated on one FPGA chip, the system
has scalability, expandability, and aﬀordable cost to construct the multi channel data acquisition system
for the Nd:YAG Thomson scattering measurement.
In this talk, we report the structure and the estimated performance of the measurement accuracy of theHYADC, and the present status of the development.
[1] Tomohisa Uchida , IEEE Transactions on Nuclear Science. vol. 55, no. 3, 2008.6, pp. 1631-1637