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Research Techniques Seminar Advances in CCD Applications with Sub Electron Noise Techniques

Research Techniques Seminar Advances in CCD Applications with Sub Electron Noise Techniques. Juan Estrada, Gustavo Cancelo 07/19/2011. R&D Projects. General CCD R&D will benefit the following projects: DAMIC . Neutrino coherent scattering experiment ( ν CCD). Neutron imaging.

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Research Techniques Seminar Advances in CCD Applications with Sub Electron Noise Techniques

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  1. Research TechniquesSeminarAdvances in CCD Applications with Sub Electron Noise Techniques • Juan Estrada, Gustavo Cancelo • 07/19/2011

  2. R&D Projects • General CCD R&D will benefit the following projects: • DAMIC. • Neutrino coherent scattering experiment (νCCD). • Neutron imaging. • Spectroscopy for astronomy. • CCD fast readout.

  3. Recent papers • 1. arXiv:1107.0925 [pdf] Title: Deep sub electron noise readout in CCD systems using digital filtering techniques • Authors: Gustavo Cancelo, Juan Estrada, Guillermo Fernandez Moroni, Ken Treptow, Ted Zmuda, Tom Diehl ), to be submitted to Experimental Astronomy. • 2. arXiv:1106.1839 [pdf, ps, other] Title: Achieving sub-electron readout noise in Skipper CCDs • Authors: Guillermo Fernandez Moroni, Juan Estrada, Eduardo E. Paolini, Gustavo Cancelo, Stephen E. Holland, H. Thomas Diehl ), to be submitted to Experimental Astronomy. • 3. arXiv:1105.5191 [pdf, other] Title: Direct Search for Low Mass Dark Matter Particles with CCDs • Authors: J. Barreto, H. Cease, H.T. Diehl, J. Estrada, B. Flaugher, N. Harrison, J. Jones, B. Kilminster, J. Molina, J. Smith, T. Shwarz, A. Sonnenschein • 4. arXiv:1105.3229 [pdf, other] Title: Plasma effect in Silicon Charge Coupled Devices (CCDs) • Authors: Juan Estrada (Fermilab, USA), Jorge Molina (FIUNA, Paraguay), J. Blostein (CAB, Argentina), G. Fernandez (UNS, Argentina), submitted to NIM. • 5. arXiv:0911.2668 [pdf] Title: Direct Dark Matter Search using CCDs • Authors: Juan Estrada • In preparation: • 12 channel readout results. • Full well problem in DECam CCDs results • Many conference presentations.

  4. Collaborators • Fermilab: • J. Estrada, T. Diehl, H. Cease, D. Kubik, G. Derilo, K. Kuk, K. Schultz, A. ?, W. Struemer T. Shaw (PPD team) • G. Cancelo, T. Zmuda, K. Treptow, N. Wilcer, J. Chramowicz, (CD team) • Vic Scarpine (AD) • B. Kilminster, J. Smith, T. Schwarz, A. Sonnenschein (DAMIC) • J. Molina • Facultad de Ingeniería, Universidad Nacional de Asunción, Asunción, Paraguay • J. Blostein, others • Centro AtómicoBariloche and InstitutoBalseiro, • ComisiónNacional de EnergíaAtómica, Universidad Nacional de Cuyo, Bariloche, Argentina • G. Fernández, E. Paolini • Universidad Nacional del Sur, Bahía Blanca, Argentina. • Javier Castilla, CIEMAT, Madrid Spain. • N. Harrison: Naperville North High school, now freshman at University of Chicago • S. Wagner: Naperville North High school. • J. Jones: Batavia High School, now at Purdue. • Jacob Johansen • University of Chicago • Possible collaborators: • Juan Carlos D’Olivo , Alexis Aguiler (UNAM, Mexico) – interest in reactor experiment with CCDs in Mexico • Helioda Motta, Carla Bonifazi, Martin Makler (CBPF, UFRJ) interest in reactor experiment with CCDs in Angra. • Requested a grant to CONICET, Argentina (Mayosky, Cancelo)

  5. Outline • Introduction to CCDs. • Sub electron noise results. • Fast readout results. • Applications: • Neutron imager. • DAMIC. • Neutrino coherent scattering. • Spectroscopy for astronomy.

  6. Charge Coupled Devices (CCD) Potential well • Characteristics: • Properly biased CCDs store charge in a potential well. • Very low noise detectors => high dynamic range. • 1e- of noise RMS => 3.6eV ionization energy. • High spatial resolution: 15 x 15 micron pitch for DeCam CCDs. • High density: 8Mpix for DeCam CCDs.

  7. Optical characteristics of LBNL CCDs used for DES DECam: High resistivity, 250µ thick. Fully depleted! Photon Transfer Curve (PTC) High QE in near infrared. Z>1 1g of mass, good for direct DM search. p-channel, better than n-channel for space telescopes • Photon Transfer Curve: • Full well • Readout gain • Pixel and dark current non uniformity • more... Low resistivity CCDs

  8. Dark Energy Camera (DECam) New wide field imager for the Blanco telescope (largest focal plane in the southern hemisphere) Largest CCD project at FNAL. DECam is being built at FNAL including CCD packaging, full characterization, readout electronics. CCD facilities at SiDet and 5+ years of experience positions FNAL as a leader for this task. Blanco 4m Telescope Cerro Tololo, Chile Mechanical Interface of DECam Project to the Blanco CCD Readout Filters Shutter Hexapod Optical Lenses Focal plane with 74 CCDs (~600 Mpix). All the scientific detectors in hand, packaged and characterized at FNAL.

  9. Low noise is critical in spectroscopy DECam estimates redshift from the colors of the objects. DeCam used 4 filters DeSPEC spectrograph proposal: Lower signal to noise ratio. X000 fibers 4 DES filters colors change as galaxy moves in z several spectrographs

  10. Low noise CCD readout • A low noise CCD based readout system will greatly benefit projects such as: • Direct search for Dark Matter • Neutrino coherent scattering. • Spectroscopy. • Two Low noise reduction techniques: • Reduction of Pixel to pixel correlated noise using fast sampling, precision A/D conversion and digital filtering. • Skipper CCDs.

  11. Outline • Introduction to CCDs. • Sub electron noise results. • Fast readout results. • Applications: • Neutron imager. • DAMIC. • Neutrino coherent scattering. • Spectroscopy for astronomy.

  12. HORIZONTAL REGISTER H1 H2 H3 VREF VDD Summing Well Transfer Gate Reset Pixel period VERTICAL CLOCKS Output JFET VIDEO AMPLIFIER 3-PHASE ARRAY CCD CGS e- e- e- Video Out. Pixel charge e- Cs Load Resistor Pedestal VERTICAL CLOCKS VIDEO AMPLIFIER e- e- e- HORIZONTAL REGISTER H1 H2 H3 CCD Images Reset pulses are ~ 50,000 e- FITS image: Each pixel is a n-bit digital representation of the pixel charge.

  13. CCD noise: single video transistor and system noise • Red trace: CCD noise measured by the LBNL designers using a test board. • 1/f noise larger than WGN up to 50 KHz. • WGN about 10nV/√Hz. • Black trace: FNAL 24 bit ADC based system. • x3 lower noise than the Monsoon system used for DeCam (DES). • Despite power supply and EMI noise reduction the system still shows some 60Hz and high frequency resonances.

  14. Video fragment: Npix pixels and Npix pedestals long. Pixeli Pedestal i Pedestal i+1 Pixel i+1 Correlated Double Sampling (CDS) Integration intervals: t4-t3 = t2-t1 = T x(n) = s(n) + n(n) + w(n) s(n) pedestals and pixels n(n) correlated noise (LFN) w(n) white Gaussian noise For the white and Gaussian noise w ~ N(0,σ²), the CDS is the optimum estimator. but It actually grows for longer T because the 1/f noise grows exponentially as f->0.

  15. CDS transfer function • The CDS filters very low frequency noise close to DC. • Minimum noise rejection at f~0.4/TPix. • Nulls at f=k/TPix, where k=1,2,3,… • Better filtering for higher frequencies. • Transfer function maximums follow a |sin(x)/x| decay. Tpixis a “free” parameter. In the analog CDS we adjust Tpixfor the minimum noise where the 1/f contribution is small. But short Tpix limit WGN reduction. So far analog CDS techniques achieve ~2e- of noise at Tpixof ~20useconds.

  16. Estimator and digital CDS • Digital sample the video signal. • Estimate the correlated noise of a string of pixels. • Subtract the correlated noise from the original video. • Perform the digital CDS of the filtered signal. • χ2 estimator, because it does not assume a particular noise model: • Inversion of a large matrix.Only one time and can be done off-line. • Linear model is not orthogonal. Ill-posed problem. • Goal: • Implement the estimator and the digital CDS in an FPGA. Create FITS image. We can eliminate the pedestal and pixel values si from the estimation problem. where <x(n)> is the average signal+noise value in each pixel (step function) New linear model: where θ is a px1 vector y(n) x(n)

  17. How many modes? Noise spectrum weighted by the CDS transfer function Cumulative noise spectrum weighted by the CDS transfer function • 200 modes account for ~85% of the low frequency correlated noise. • If parameter estimation could be done with zero error.

  18. Estimator and digital CDS Results (DeCam CCD) • 0.5e- of noise achieved (consistently) for Tpix of 70useconds.

  19. Estimator and digital CDS Results (LBNL 12 channel CCD) • The plot displays the average noise of 100 data sets and 1-σ error bars. • 0.4e- at 120 μs. • It is also interesting that the 1-σ error bars of the estimator processed data are 4 times smaller than the ones for the unprocessed data.

  20. Noise spectrum comparison • Compares the noise power spectrum of the unfiltered signal and the filtered signal after the low frequency estimation of 200 modes has been subtracted. • On average, the LFC noise has been reduced by almost an order of magnitude on average.

  21. FPGA implementation of the estimator and digital CDS X-ray image using a 55FE source CCD Overscan • The implementation of the estimator in the FPGA is on going. • In this image the FPGA is performing the digital CDS with noise results very similar to the off-line results.

  22. Skipper CCD skipper CCD mounted on one of our testing dewars.

  23. Skipper CCD these type of detectors allow multiple readout of the charge in each pixel, with a noise reduction 1/sqrt(N). I was invented in 1990, but not really used much because it takes more time to readout. in a recent R&D run LBNL produced thick detectors like this, and sent them to us for testing. They are very interesting for low threshold experiments...

  24. Skipper CCD Frequency response for: Tʃ = 110 µs and N = 5 (a), N = 10 (c) and N = 20 (d), T ʃ= 160 µs, and N = 10 (b). Left axis: CCD noise PSD (a). Standard CDS Tʃ = 110 µs (b) Skipper CDS Tʃ= 110 µs and N = 10 (c).

  25. what have we done with the skipper: > built the cables to readout the skipper > programmed the controller to operate this new CCD > started tests > this is the main topic of the work that Jacob Johansen is doing as part of his graduate class at UC x-ray exposure CCD x-ray hits look like small horizontal bars in the image because the same pixel is readout many times. Skipper CCD e− RMS as a function of the number of averaged samples N. Continuous line: e−RMS measured from images. Dashed line: theoretical 1/√N decay of WGN.

  26. Low-energy X-ray detection experiment with the Skipper CCD. First time this peak is seen with a CCD • Fe55 X-ray source and a teflon target • A shielding is placed between the source and the CCD for stopping direct X-rays. • The Fe55 X-ray source produces two different energy rays from Mn: 5832 eV (K α ) and 6412 eV (K β ). Both X-rays hit the teflon with carbon and fluorine, which emits lower energy X-ray by fluorescence. • Each atom has a precise energy pattern of emitting photons, the most probable emitted X-rays are at energies of 277 eV and 677 eV, respectively. • These low-energy X-rays are detected by the CCD together with some high energy X-rays • coming directly from the source that get to cross the shielding.

  27. Skipper paper: http://arxiv.org/PS_cache/arxiv/pdf/1106/1106.1839v2.pdf • what is next with skipper: • 1. Optimization of readout for operation with extremely low readout noise • 2. We need to get more detectors packaged with low background package and start DM run at minos.

  28. Summary and future work for CCD low noise readout • The estimator and digital CDS reduce the CCD noise deep into the sub-electron region. • New avenues for HEP experiments and telescopes are open: • The price to pay for lower noise is a more sophisticated readout system. • The estimator and digital CDS is being implemented in an FPGA with good success.

  29. 12 channel LBNL CCD 6 • This CCD would be a good candidate for telescopes that require high pixel bandwidth such as LSST.

  30. 12 channel LBNL CCD 12 channel CCD detector arrived on October 3 from LBNL stage 1: readout the CCD using the DECamelectronics with minimal modifications . Show that we can do it and use results to motivate FNAL management to support this R&D effort. Done on Octber 13! stage 2: make necessary modifications to readout the 12 channels with DECam performance (250 kpix/sec and 8 e- of noise). Use the DECam 12 channel monsoon board and a new cable for the 12 channel CCD (with 12 JFETs and 12 preamps). Required design of preamp board and flex cable. Completed in January 2011. stage 3: works towards more aggressive performance thinking in LSST requirement. Study the high readout rate limitations of the devices. Readout rate could be increase by digitizing during the horizontal clocking. Started in mid-January. Javier Castilla, from CIEMAT (DECam collaborator) expert on monsoon system came to FNAL work on this for two months. FNAL R&D effort support this now. Javier Castilla will return to Fermilab in December using funds from his home institution.

  31. stage 1: Installation of 12-channel CCD in Cube. Simple flat ribbon cable used to connect to the CCD. No JFET installed.

  32. Results stage 1: first readout. 12 channels connected to the DECam 12 channel readout board without any conditioning for the signal. For DECam we use JFET next to the CCDs and preamps inside the dewar. We got 11 out of the 12 channels to work. Very noisy readout low gain. second readout. 2 channels connected to the DECam 8 channel prototype readout board with preamps outside the dewar. The readout worked and got ~20e of noise at 250 kpix/sec.

  33. flatfield of 2 channel readout using prototype decam boards. nice cosmetics!

  34. channel 1 (left) photon transfer: we obtain a gain of 0.47ADU/e. (typical gain for DECam CCDs with JFET and preamp is 0.8 ADU/e). fullwell at 89,361e-. (consistent with area reduction with respect to DECam pixels)

  35. Setup in SiDet Lab A

  36. Images taken with a 12 channel Monsoon system

  37. 12-channel :Pixel cycle time 1.85us Pixel cycle: 1.848 us INTEG_WIDTH = 2*500 ns Noise : 10.7 e-

  38. At slow readout the noise performance is comparable with DeCam CCDs

  39. Outline • Introduction to CCDs. • Sub electron noise results. • Fast readout results. • Applications: • Neutron imager. • DAMIC. • Neutrino coherent scattering. • Spectroscopy for astronomy.

  40. Neutron imager why neutrons? Potential SRF accelerator application? Key tool for Basic Energy Science. Hydrides may be a major player in Rresand Q0. (A. Romanenko, FNAL)

  41. Example of a beam of collimated low energy (thermal) neutrons (NIST CNR facility). The image resolution is a function of many parameters, some of which are improved by the 10B-CCD detector. We need high quality beams to make full use of high resolution detectors. The plasma experiment (a slide coming next) shows that 1um resolution is achievable.

  42. state of the art 10B-CCD the CCDs would allow us to achieve micron level resolution and at the same time 1 frame per second....

  43. our scheme... CCD Motivated by conversations with neutron physics group in argentina during ICFA 10. Thanks to the R&D funding we were able to do the preliminary test at FNAL inviting Dr. Jeronimo Blostein.

  44. First test with Am-241 source. The CCDs are really nice alpha detectors alphas big circles x-rays small dots • Image taken with neutron 252Cf source, 5um film of 10Boron and CCD alphas big circles

  45. good separation from gammas

  46. 1st test, December 2010 Borated film (3mm from CCD) borated film deposited in laboratory in argentina Cd target (8mm from CCD)

  47. lines in borated film Cross in Cd

  48. Plasma effect measurement Our data Best current measurement 2008 Energy dependence of the cluster size for α particles in both regions of energy. Red points are for the exposition of the CCD to the 241Am source, while black points are for α particles coming from the (n,α) reaction Plasma effect in Silicon Charge Coupled Devices (CCDs), J. Estrada, J. Molina, J. Blostein , G. Fernández. http://arxiv.org/PS_cache/arxiv/pdf/1105/1105.5191v2.pdf

  49. 2nd test, July 2011 (work by Sebastian Wagner, sophomore student at Naperville North high school) • A factor of 4 better resolution 2nd exposed surface 1st exposed surface Bottom half of open cross

  50. Last minute result July-19-9am

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