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Spectrap Electronics Evaluation of Cryogenic Components Begin 2009

Spectrap Electronics Evaluation of Cryogenic Components Begin 2009. Stefan Stahl measurements by Stefan Stahl & Zoran Angelkovic. m · D². t =. q² · R. Preface: main objectives. Resistive Cooling of captured ions to T = 4.2K and ion detection.

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Spectrap Electronics Evaluation of Cryogenic Components Begin 2009

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  1. Spectrap ElectronicsEvaluation of Cryogenic Components Begin 2009 Stefan Stahl measurements by Stefan Stahl & Zoran Angelkovic

  2. m · D² t = q² · R Preface: main objectives • Resistive Cooling of captured ions to T = 4.2K and ion detection challenge : important to have low final temperature=> new amplifier design • Rotating Wall Compression • FT-ICR Detection (optional) challenge : FT-ICR and rotating wall compression at the same time

  3. Novel Amplifier Design • FET with low input capacitance => low heating of LC circuit • Additional cascode circuitry further lowers CIN Main former problem (GaAs-FETs) : 1/f-noise and input capacitance lead to increased axial ion temperature of 30 – 70 K (see: g-factor experiments, Gabrielse-setups)

  4. Noise Chart of designed amplifier Using NEC 3508 „super low noise“ HJ-FET (GaAs) • LC circuit at trap will show about 22nV/(Hz)1/2 @ 2MHz • Cin determined to 1.8pF • strong decoupling 6:1 possible Presumably low Tnoise~ 6K

  5. T = 4.2K non-linear filters reduce noise and allow FT-ICR at the same time Low pass functionality, overruled at high amplitudes Rotating Wall Compression T = 300K Established 2008

  6. Frequency and Amplitude response Observations: General functionality verified Clear Voltage Threshold as expected Output Excitation amplitudes somewhat too low Failure of diodes at Uin ~ 12Vpk or 240mApk => modifications will be tested coming weeks

  7. Geometrical Arrangement

  8. Another Idea: Charge Detector for Adjustment Sensitive cryogenic charge amplifier on back side

  9. Summary and Outlook • Low input capacitance amplifier design verified and tested => suitable for axial detection and resistive cooling • Filter unit successfully tested; some weak point discovered, to be solved soon • Several components (capacitors, resistors, diodes and FETs) verified for compatibility with 4.2K environment • Refine overall circuitry design and adapt to latest geometrical changes • Eventually add functionality of cryogenic destructive charge detector • Test of completed cryo setup after connecting the trap and room temperature electronics • Software control of devices

  10. Thanks a lot for your attention. Email:s.stahl@stahl-electronics.com www.stahl-electronics.com

  11. Spare Slides:

  12. Examples of Coil-Design

  13. x y Detection of Image Charges, FT-ICR Pickup-Elektrode Pickup-Elektrode

  14. x y Detection of Image Charges, FT-ICR Pickup-Elektrode ion current signal I t Pickup-Elektrode

  15. Signal strength x y D ~ distance of pickup electrodes very small signal ~fA Detection of Image Charges, FT-ICR Pickup-Elektrode ion current signal I Pickup-Elektrode

  16. x y very small signal ~fA Detection of Image Charges, FT-ICR Pickup-Elektrode q/m spectrum ion current signal I I f t „FT-ICR“ Fourier-Transform Ion Cyclotron Resonance Pickup-Elektrode

  17. Detection of Image Charges, FT-ICR • Method is non-destructive • Many ion species can be detected at the same time • Small sensitivity to space charges compared to TOF • Useful over a very wide range of ion numbers

  18. FT-ICR Circuitry

  19. First H2O+ Resonance:

  20. Shot Noise by Ions and Electrons Creating shot noise while flying through  1010 electrons/sec. ~ 6 fA/ (Hz)1/2  1012 ions/sec. ~ 700 fA/ (Hz)1/2

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