Mullard Space Science Laboratory A CCD in place
Mullard Space Science Laboratory A CCD in place of an MCP: Using a CCD for the direct detection of electrons in a low energy space plasma spectrometer Robert Bedington – Ph. D Student Dhiren Kataria & Dave Walton -Supervisors
Mullard Space Science Laboratory Overview • • • Miniaturised electron analyser CCD Experimental setup Analysis methods and results A proposed student instrument 2
Mullard Space Science Laboratory CATS – Conceptual And Tiny Spectrometer CATS + CCD • CATS analyser head – uses electrostatic optics to transmit particles of different energy bandpasses out different apertures onto a detector • Usually an MCP or CEM detector is used. We are experimenting with using a CCD as these can be easier to work with. 3
Mullard Space Science Laboratory CCD – E 2 V CCD 64 -00 • • CCD image frame Integral Mission spare E 2 V x-ray special order back thinned Full Frame 1 nm dead layer Not ion implanted Tested with laser cut mask of UCL logo and Nickel radioactive source. • …which caused permanent damage CATS aperture area 4
Mullard Space Science Laboratory Experiment aims • Imaging electrons at the CATS apertures • Verifying previous CATS Angular and Energy calibrations • Assess suitability for a sounding rocket instrument 5
Mullard Space Science Laboratory Experimental Setup Thermally conductive braid Photocathode Liquid Nitrogen Side schematic: Vacuum Chamber and Mu metal case CATS + CCD Elevation motor CATS and CCD Data and electrical connections Voltage applied to electrodes Azimuth motor MSSL electron analyser calibration chamber 6
Mullard Space Science Laboratory CCD Energy Response Varying electron beam energy whilst adjusting CATS accordingly. Mulassis (GEANT 4) simulations Penetration of 500 e. V electrons into CCD 200 180 140 120 100 80 60 Dead Layer Energy Deposited (e. V) 160 Reduced CCE region 40 20 0 0 Each data point is nine CCD frames summed. Each frame is ~4 second acquisition 2 4 6 8 10 Depth from back layer (nm) 12 14 Full simulations performed by another student at MSSL 7
Mullard Space Science Laboratory Images of Electrons exiting CATS analyser head: Two different techniques Composite images of multiple CATS Voltages/angles ‘Long’ Integrations Showing ‘A’ Channels here • ~3 sec acquisitions • scaled background frame removes dark current and UV • • ‘Short’ Integrations Showing ‘B’ Channels here 1000 frames per step 1 frame ~10 ms acquisition Averaged frame removed and individual electron events extracted (less stable) 8
Mullard Space Science Laboratory CATS analyser - Voltage and angular calibrations Take total counts in aperture areas at each voltage/angular step to produce calibrations Counts (ADU) Some rough results as examples: Different peaks here refer to different CATS channels Angular scans for a single channel 9
Mullard Space Science Laboratory Pole. CATS – CATS and CCD on a sounding rocket • REXUS student flight – launch 2013 CCD Advantages Disadvantages Low voltages Higher KE electrons only No Vacuum requirements Cooling issues Ready and available Sensitive to light • Recruitment of students – Instrument Development/ Mechanical / Science / Outreach • Sponsorship – Funding & donated components • FPGA, CCD, cooling etc • http: //rexuspolecats. com 10
Mullard Space Science Laboratory Summary • CATS is a miniaturised plasma analyser head • CCD directly detected and imaged electrons at its exit apertures • CCD is sensitive to electrons with KE > 500 e. V • Effective detector for laboratory calibrations • Effective detector for space based instruments? – TBC http: //rexuspolecats. com 11
- Slides: 11