Cameras: DIII - Dust imaging - Phantom v7.1 CMOS but with Coherent fibre bundle. NSTX/DIII-D Fast Framing camera CMOS > 4500fps but 256x256 or less survives 250mT on NSTX and 50mT on DIII-D camera in radiation shield and used 2.7m fibre bundle outside fibre bundle browned and died after 200 shots in DIII-D Camera survived two campaigns on NSTX before significant noise and CMOS sensor replaced. NSTX 1e14 neutrons / sec on DIII-D ~ 100x NSTX, so ~ 1e17 Radiation shielding for camera of borated polyethene ~30cm Gamma rays from neutron-gamma reactions in structures also significant on electronics, used DIII-D can operate up to 5e16 n/s. Particle accelerators use CCDs instead of th SVDs sometimes for initial particle tracks. They investigate ~1e15, 1e18 n/m2 (presumably total) Typical Neutron fluences: W7X: ~ 3.5e13 n/cm²/year at camera ports., about ½ is 2.45MeV. [Nafradi/Kocsis "Radiation Damage In Video Diagnostic Device for W7X"- EPS 2 http://epsppd.epfl.ch/Hersonissos/pdf/P5_079.pdf ] for w7x, this is rather good: [J.Andersson - "Simulation of neutron uxes around the W7-X Stellarator"] Dark Current Grows with fluence linearly. [Amaden and Nafradi/Kocsis] [Amaden - "Fusion Neutron Damage to a Charge Coupled Device Camera" http://www.dtic.mil/cgi-bin/GetTRDoc?Location=U2&doc=GetTRDoc.pdf&AD=ADA339378 ] Thesis, lots of detail. Used EEV 1152x1242 CCD camera. 14MeV neutrons under a direct test. Dark curent grows with neutron fluence Up to 6.6e12 n/cm² in small steps. [ M.Angelone "Time Dependent 14 MeV Neutrons Measurement Using a Polycrystalline CVD Diamond Detector at JET Tokamak" ] The ratiobetween 2.5MeV and 14MeV and 2.5MeV neutrons for D-D plasmas is about 0.0199... "can withstand 14 MeV neutron flux higher than 3e8 n/cm2 s), still operating in a linear mode [6]. These fluxes are those expected, for example, around the JET tokamak when it is operating with D-T plasmas." " was able to detect the 14MeV neutron emissions ( >1.0 x1015 n/shot)" [ L. Giacomelli "The compact neutron spectrometer at ASDEX Upgrade" ] Their detector sees about 1e5 n/s and sits at R=~12m Mostly 2.45MeV AUG YnTOT ~ 1e15 YnTOT /s ~ 1e14 Total yield is ~ 1e14 s^-1 K-STAR radiation assesment says around 10^16 n/s total [HyundukKim "Radioactivity evaluation for the KSTAR tokamak" http://rpd.oxfordjournals.org/content/116/1-4/24.full ] Our camera is at R=4.25m, 2.6m from centre of plasma Surface area of sphere = 4 pi R^2 1cm^2 / (4 pi R^2) ~ 4.5e-7 Surface area of torus = 4 pi^2 R r with R = 1.65m and r = 2.6m (yes, I know r > R but... meh) 1cm^2 / (4 * pi^2 * 1.65 * 2.6) ~ 6e-7 So neutrons at camera ~ 6e7 n/cm^2/s Probably at worst 10^8 n/cm^2/s. W7X was claiming 10^13 n/cm^2 at cameras in ports (ok similiarish +/- 1 order) per year of operation lets say 10^4 seconds of operation (that produced neutrons) per year = 10^9 n/cm^2/s [ http://www.pppl.gov/~neumeyer/SOFE/Presentations/SO2/SO2B-1%20Sykes.pdf ] Presentation by the MAST ppl about their ST neutron source plans Full CTF: 10^19 n/s MAST: 10^14 n/s MAST-U: 10^15 n/s [ Handbook of CCD Astronomy http://books.google.co.uk/books?id=ZZCTqanpsZUC&pg=PA176&lpg=PA176&dq=ccd+gamma+ray+damage&source=bl&ots=sSpscqzgpn&sig=EGb6aqTfXbLhDg0D7CT3Y9RJkgI&hl=en&sa=X&ei=lXJxT7z3LYOLswaBktHZDQ&ved=0CEcQ6AEwBA#v=onepage&q=ccd%20gamma%20ray%20damage&f=false page 176 ] "... Galileo's RTG produced 10^10 neutrons per square centimeter at the locations of the CCD over the expected siz-year mission lifetime. Passage through Juipter's radiation belts near the moon Io was predicted to provide a 2500 rad dose of radiation to the CCD with each orbit. These leavel of radiation do indeed cause damage to the CCD involved and methods of monitoring the changes that occur with time and the development of new manufacturing techniques aimed at radiation hardness were needed (McGrath, 1981) The two majro areas of concern in radiation damage to the CCDs are (1) high energy photon interations, which result in fast electrons, which in turn cause simple, localized damage defects and the generation of numerous electron-hole pairs and (2) nuclear reactions caused by uncharged neutrons or high energy protons, which cause large area defects and are more likely to lead to partial or complete failure of a device (Janesick, Elliott, & Pool 1988: Janesick 2001). The first of these radiation induced concerns is called an ionization effect and involves gamma rays or charged particles. The second, involving massive particles, is terms a bulk effect or displacement damage owing to its ability to displace silicon atoms from their latter positions within the CCD. " "The SAA [South Atlantic Anomaly], for example, provides about 2000 protons per square centimeter per second with energy of 50-100MeV for each passage" 2500 rad = 25gray = 25 J /kg if CCD ~few g, depositied ~ 0.025 J = 10^10 x 10^10 MeV gamma rays - yikes The CID cameras were claiming to cope with ~Mega Rads: 10^6 rad = 10^4 gray A few g CCD --> 10^12 20MeV gammas, or 10^13 2MeV neutrons - which is great. CTE = charge transfer efficiency Notes from reading up on fusion neutron/gamma damage to CCDs. (mainly 2.45GeV DD neutrons) [ E-mails from Giovanni Tardini at ASDEX ] "we can reach fluxes up to 1e15 n/s but yes, a few 1e14 is the usual case. The signal of the yield is ENR:NRATE_II, usually it is automatically available." "As for the estimate, one needs the geometry, in particular which is the "aperture" (from the neutron point of view) of the parts of the camera that can be damaged. As a crude astimate one can assume the neutrons are all emitted from the torus center and then check which fraction of the 4 pi solid angle are relevant for crossing the CCD. This is not very accurate, because parts of the structure screens the CCD from neutron; the error from the geometry is not as dramatic, because at R=4.25 m the angle is small and the approximation of "point source" is acceptable. So let's put numbers: 4 pi R**2 ~ 2e6 cm**2 I expect a maximum of 1e9 * CCD_cross_surface [cm**2] neutrons/sec " so yes, about 10^8/10^9 n/s/cm^2 for us [ J.Harheusen "Interpretation of Dα Imaging Diagnostics Data on the ASDEX Upgrade Tokamak" ] Dissertation "The cameras are mounted at a distance of about 3.5 m to the plasma core, restricted by the length of the image guide, and are shielded by 30 cm Lithium carbonate added paraffine and 5cm Lead to attenuate the neutron flux and the γ-radiation. However, in particular during high power plasma discharges, energetic particles may reach the detector and produce saturated pixels. Due to the hard radiation exposure during an experimental campaign, the CCD-chip is observed to deteriorate. This meansthat the number of pixels, which appear to be less or more sensitive or even are permanently saturated, increases. What is described as a higher sensitivity is probably in fact an increased dark current due to defects in the semiconductor structure." This also contains lots of juicy data about neutrons effect on the fibre image guides, which is pretty bad too. [ ??? via Christoph Biedermann at Greifswald (e-mail) - CMOS sensor Irradiation tests for W7X ] Subjected CMOS sensor to: 10^12 gammas of "> 1MeV": No lasting damage, flashes. 10^12 neutrons of "> 1MeV": pixel dark current increase, but doesn't look too bad. [ J.M.Kiliany - "Radiation Effects in Silicon Charge-Coupled Devices" Topics in Applied Physics, 1980, Volume 38/1980, 147-176, DOI: 10.1007/3-540-09832-1_6 http://www.springerlink.com/content/y648h4744408x22t/ ] Thorough theory of it all, but a bit old (1980). Most of it seems to be about 'burried channel devices' Near the top: "The type of displacement damage produced in silicon is a function of the radiation species. Gamma rays and electrons of a few MeV produce simple defects which are best described as a distribution of point defects. The present model for bulk damage in silicon resulting from neutron bombardment is the formation of superclusters, each containing a number of highly damaged regions (superclusters)." Neutrons are covered under 'Displacement Damage Effects': "Hartsell observed that increased trapping effects in neutron-irradiated n-buried channel CCDs are insignificant for fluences less than 10^11 n/cm^2. Saks et.al. reported a linear CTE increase in the 10^11 to 10^13 n/cm^2 range (~15MeV average). After 10^13 n/cm^2 the CTE at 295K was reduced to 0.992 making the devices unsuitable for most applications. From the work of Smith et. al, the degrdation measured after 15MeV neutron bombardment is expected to be 2.5 to 3 times greater than the value for a 1MeV equivalent neutron fluence." ... " the fraction for gamma rays is smaller. ... Hence bulk damage effects due to gamma irradiation are insignificant for doses less than 10^6 rads (i.e. 2x10^15 1MeV gammas / cm^2)" ... "Saks et.al. observed an approximate linear increase in the dark current density in the 10^11 - 10^13 n/cm^2 (15MeV average) range for an n-buried channel structure" [ e2v centre for electronic imaging http://www.open.ac.uk/pssri/cei/?p=0 ] Some kind of open university thing which a particular interest in radiation hardness of sensors and sensor development (space). [ A.C.Maas - "Diagnostic Experience during Deuterium-Tritium Experiments in JET, Techniques and Measurements" http://www.iop.org/Jet/article?JETP9811&JETP98080 ] Brilliant. Just read section 2.4 onwards. Basically, during DD they had 2 cameras, one on an endoscope and one direct. The direct one was replaced after every 3000-4000 pulses, one year, roughly 3x10^11 n/cm^2 at 1MeV equiv. "No noticable deteioration to the camera fitted to the endoscope after ~4000 pulses" DT ~ DD * 100 for expected damage. Both were removed for DT and a wide angle CID camera installed directly viewing. After DT campaign, it had seen about 4*10^14 n/cm^2 (at 1MeV equiv) and had a "significant increase in dark current" "The main disadvantage of CID cameras for tokamak applications is that they are very sensitive to magnetic fields" ... so ... err ... there doesn't seem to be any consistent picture or concensus emerging. Fields ---------------------------- Pixelfly both QE+VGA were tested up to 3T multi orientation - W7X IPP EDICAM - 1/4 QE of pixelfly, ~ 15% EDICAM are the CMOS cameras planned for w7x (via the Hungarians) These are also being tested by 'Gabor' at ASDEX. From Robert ---- Albrect Herrmann - ASDEX cameras Tilman Lund - wide angle Tilmann Kunt: AUG VRT - Real Time Video (Tilmann Lunt) Sentech 90fps VGA Jai B/W 10bit 120Hz Sentech B/W 12-bit 2448x2058 16Hz