Tracer-Encapsulated Solid Pellet (TESPEL)
Naoki Tamurae-mail: tamura.naoki@nifs.ac.jp
1. Purpose
A Tracer-Encapsulated Solid Pellet (TESPEL) is a double-layered impurity pellet, whichbasically consists of polystyrene polymer (-CH(C6H5)CH2-) as an outer shell and tracer
particles as a core. TESPEL can be utilized for various physics-oriented experiments, e.g.
impurity injection for the perturbative impurity transport, induction of a cold pulse
propagation, and so on.
2. Name of analysis (Kaiseki) data / module of MyView2
2.1. Retrieve
Diagnostic Name = “TESPEL”
2.2. Kaiseki-data server
Diagnostic Name = “TESPEL_abl”
2.3. Module of MyView2
Currently, not available.
3. General descriptions
3.1.

TESPELØ Outer diameter: 400 ~ 900 µm
Ø Tracer material: It can be utilized as a tracer as long as it
is solid. 43 kinds of elements (from Li (Z=3) to Lu(Z=71)) have been used as a tracer of the TESPEL in themagnetically-confined high-temperature plasmas.
Ø Typical tracer size: 100 ~ 200 µmf
è Resulting typical deposition width of the tracer: 2 ~ 3cm
3.2.

Fig.1 Photo of TESPEL

Injector (#1(TESPEL4) from 3O-BC01-01(being prepared), #2(TESPEL2) from3O-BC-06-02)

Uniqueness of the TESPEL Injector #1: Double straight injection lines (see Fig. 2)
Ø This injector (TESPEL4) has double straight injection lines, which are located on theequatorial plane of the LHD vacuum vessel.

ØTESPEL4 is currently being prepared, and it will be available from 22nd LHD
campaign.

Fig. 2 A vertical projection view of the TESPEL4. Both injection lines are located on the equatorial
plane of the LHD vacuum vessel.

Uniqueness of the TESPEL Injector #2: Single oblique injection line (see Fig. 3)
Ø This injector (TESPEL2) has curved guide tubes to achieve an oblique injection of theTESPEL into the LHD plasma. In TESPEL2, one injection line is available.
Ø The deposition location can be varied by changing the position of the final guide tube,
which is located inside the vacuum vessel of LHD.

Fig. 3 A vertical projection view of the TESPEL2 with cross-section of the plasma and vacuum vesselof the LHD. The remote-controlled drive mechanism can move the final guide tube of the TESPEL2
upward and downward. Consequently, the expected location of the tracer deposition with theTESPEL2 is ranged from the location at reff/a99 ~ 0.4 (in the case with Rax = 3.75 m) to that outside thelast closed flux surface of the LHD plasma, i.e., inside the edge ergodic region.

Common features of the TESPEL injectors
Ø Necessary time interval to inject another TESPEL from the same disk: About 1 min.
Ø By using the TESPEL4, the time interval to inject the second TESPEL will be greatly
decreased, but a minimum interval between two TESPEL injections remains to beclarified (the minimum interval will be investigated in the 22nd campaign).

Ø Available number of the TESPEL per disk: 59 or 89 pieces
l If you need a larger number of TESPEL, please consult with the person in charge
beforehand.
3.3.

Observation system for the TESPEL ablation cloud (3O-AL01-02, 3O-AL01-03,

3O-BC01-03, 3O-BC01-04)
Photo-multiplier tubes (PMTs) and fast camera are used to measure the behavior of theTESPEL ablation.
3.3.1. PMT diagnostics
The PMTs are basically filtered (e.g., Ha, C I) according to the materials in the TESPEL.
Ø Typical temporal resolution: 1 µs
3.3.2. Stereoscopic Fast camera diagnostics
An ultra-fast frame CMOS-camera (model FASTCAM SA-X2 by Photron Inc., Japan), whichis equipped with a 12-bit CMOS sensor, is used to observe a high temporal evolution of theTESPEL ablation cloud.
Ø The optical filtering on the fast camera will be done as the situation demands.
Ø Typical frame rate of the camera: 20,000 – 40,000 frames/s for 1024 x 672 – 640 x 488
pixels.
Ø A pair of stereo images is taken from different viewports, which are focused on a single
focal plane of the CMOS sensor of the ultra-fast frame camera by using a bifurcatedimaging fiber bundle.
Ø The resulting spatial accuracy in the vertical direction of the stereoscopic measurement:
at least about +/- 1 cm.
4. Requirement in use
If you need the TESPEL even without the tracer in your experiment, please contact theperson in charge (Dr. Naoki Tamura, tamura.naoki@nifs.ac.jp) in advance (at least one
month before the start of the LHD experimental campaign), because the TESPEL is ahandmade pellet and the TESPEL can be injected only by his operation.
5. Description of analysis (Kaiseki) data / module of MyView2
We are in the process of rearranging the setup of DAQ modules. If you need to know thesetup of DAQ modules, please contact the person in charge (Dr. Naoki Tamura,tamura.naoki@nifs.ac.jp).
References[1] S. Sudo, J. Plasma Fusion Res. 69 1349 (1993).

[2] S. Sudo and N. Tamura, Rev. Sci. Instrum. 83 023503 (2013).
[3] N. Tamura et al., Rev. Sci. Instrum. 79 10F541 (2008).
[4] N. Tamura et al., Plasma Fusion Res. 10 1402056 (2015).
[5] N. Tamura et al., Rev. Sci. Instrum. 87 11D615 (2016).