1 1 – Experience of diagnostics used for LH grill protection 2 – Layout of the suitable diagnostics in ITER 3 – Info on fibre optics for wave guide arc detection Report on the Diagnostics - WG4 (A Ekedahl, O Tudisco)

2 IR camera for detecting arcs in Tore Supra Choc : P C3 = 1.7MW, P C2 = 1.1MW, t = 52.7s The IR system works, but is really too slow (20 ms) to be efficient.

3 Refl. Coeff Test of H  -system for LH launcher security in Tore Supra H  signal responds more rapidly to arc than IR measurements and UV- spectroscopy of impurities. A. Ekedahl, CH/NTT (2001) H  grill IR grill Cu Fe

4 Fe23 Fe15 Bolo2 Bolo24 P LH nlnl Bolo4 RT Bolometry for LH launcher security in JET LH launcher, Octant 3 The difference Bolo2-Bolo4 gives reliable detection of arcs in front of the grill mouth. M. Goniche et al., to be presented at 18th Topical Conf. on RF Power in Plasmas, Gent (2009) Vertical bolometry, Octant 3

5 IR and VIS in parallel in all lines of sight (Presentation O. Tudisco, 1 April 2009)

6 Port space: Horizontal ports: 1, 3, 9 and 12to view the outer wall. Top ports: 2, 5, 8, 11, 14 and 17to view the inner wall. LH launcher port: 11 Time resolution: Standard: 10ms time resolution. In addition: defined zones that have up to 20  s time resolution.  Need to find out the localisation of these fast zones.  If no suitable zones, specify the need for this in the LH system design. How to distinguish an arc from ELMs: R. Reichle proposes to use also a camera in a top port, viewing the inner wall in front of the LH grill, as a complementary system to the camera in the horizontal port. The idea is that an arc in front of the LH grill can create a reflection on the inner wall. If an arc feature is seen on the horizontal camera viewing the grill and on the top camera viewing the inner wall simultaneously, then there is likelihood of an arc. Info on VIS / IR system

7 Port space: No details from R. Reichle (RO) on this yet (but info exists in PID).  If no suitable lines of sight for LH, R.R. (RO) could try to influence this choise. Time resolution: Bolometry is a slow measurement that needs to be integrated over ~200 ms. However, an intelligent acquisition system should be able to pick up large, rapid variations and treat them as abnormal events. Experience from JET: The vertical bolometry camera, situated above the LH launcher in Octant 3, has been used for LH launcher security since  Reliable measurement, but which could be optimised further. Info on Bolometry

8 Port allocation for diagnostics Project Integration Document (PID), Version 3.0, Jan 2007, Editor: J. How Upper ports: Vis / IR (inner wall?): 2, 5, 8, 11, 14, 17 H  spect (outer edge): 2 Bolometry: 8, 17 Equatorial ports: Vis / IR (outer wall): 1, 3, 9, 12 H  spect (upper edge): 12 Bolometry: 1

9 Info on the radiation damage to fibre optics Previous ITER assessment (in [1]): Optical fibres (silica) for the transmission of optical light can only be used outside the bioshield, with the exception for the transmission in the range nm, which is possible inside the cryostat volume but outside the primary vacuum window. LH window arcs: LH arc detection sensors in TS has peak sensitivity at 900 nm (IR). In addition, a study [2] shows that arcs near RF windows emit IR radiation before visible radiation, i.e. sensors should work in IR- range.  Silica fibres are OK up to the primary vacuum window. [1] R. Reichle et al., “Final Report for the EFDA contract ”, DIAG/NTT (2005) [2] D.L. Borovina et al., in Proc. of the 1999 Particle Accelerator Conference, New York (1999) p. 786

10 Irradiation tests of fibres Irradiation tests have shown that fibres do exist that could be used up to the divertor [1]  these should be OK at the rear of the LH port plug as well. [1] R. Reichle et al., “Final Report for the EFDA contract ”, DIAG/NTT (2005)

11 Get diagnostic layouts of : Fast zones of VIS / IR systems Bolometry H  spectroscopy Get in contact Spencer Pitcher (RO Langmuir probes) for design of Langmuir probes in ITER. Actions

12 WG4: Schematic layout of different diagnostic zones Antenna front 4. DATA ACQUISITION 4.1RF monitoring and fast interlocks Launcher instrumentation (primary vacuum area) Cryostat instrumentation (secondary vacuum area) Main transmission line instrumentation Klystron instrumentation 4.2Antenna front diagnostics Edge density diagnostics and control Front face monitoring and control (4.1.1)(4.1.2) (1) (4.1.4) (4.2.1) (4.2.2) (4.1.3) Main transmission line Klystron area Bio shield