Mullard Space Science Laboratory Using a CCD for the direct detection of electrons in a low energy space plasma spectrometer A CCD in place of an MCP: Robert Bedington – PhD 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 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 CATS CATS + CCD

Mullard Space Science Laboratory CCD – E2V CCD64-00 Integral Mission spare E2V x-ray special order back thinned Full Frame 1nm dead layer Not ion implanted Tested with laser cut mask of UCL logo and Nickel radioactive source. …which caused permanent damage 4 CATS aperture area CCD image frame

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 6 CATS and CCD Vacuum Chamber and Mu metal case Voltage applied to electrodes MSSL electron analyser calibration chamber Liquid Nitrogen Thermally conductive braid Photocathode Elevation motor Azimuth motor CATS + CCD Data and electrical connections Side schematic:

Mullard Space Science Laboratory CCD Energy Response 7 Varying electron beam energy whilst adjusting CATS accordingly. Mulassis (GEANT4) simulations Penetration of 500eV electrons into CCD Dead Layer Full simulations performed by another student at MSSL Each data point is nine CCD frames summed. Each frame is ~4 second acquisition

Mullard Space Science Laboratory Images of Electrons exiting CATS analyser head: Two different techniques 8 ‘Short’ Integrations Showing ‘B’ Channels here 1000 frames per step 1 frame ~10ms acquisition Averaged frame removed and individual electron events extracted (less stable) ‘Long’ Integrations Showing ‘A’ Channels here ~3 sec acquisitions scaled background frame removes dark current and UV Composite images of multiple CATS Voltages/angles

Mullard Space Science Laboratory CATS analyser - Voltage and angular calibrations 9 Take total counts in aperture areas at each voltage/angular step to produce calibrations Some rough results as examples: Different peaks here refer to different CATS channels Counts (ADU) Angular scans for a single channel

Mullard Space Science Laboratory PoleCATS – CATS and CCD on a sounding rocket REXUS student flight – launch 2013 Recruitment of students –Instrument Development/ Mechanical / Science / Outreach Sponsorship –Funding & donated components FPGA, CCD, cooling etc 10 CCD AdvantagesDisadvantages Low voltagesHigher KE electrons only No Vacuum requirementsCooling issues Ready and availableSensitive to light

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 > 500eV Effective detector for laboratory calibrations Effective detector for space based instruments? – TBChttp://rexuspolecats.com 11