Spectrap Electronics Evaluation of Cryogenic Components Begin 2009 Stefan Stahl measurements by...

Spectrap ElectronicsEvaluation of Cryogenic Components Begin 2009

Stefan Stahl

measurements by

Stefan Stahl & Zoran Angelkovic

Spectrap Collaboration Meeting, April 2, 2009

Spectrap Evaluation of Cryogenic Components

Preface: main objectivesPreface: main objectives

challenge : important to have low final temperature=> new amplifier

design

• Resistive Cooling of captured ions to T = 4.2K and ion detectionResistive Cooling of captured ions to T = 4.2K and ion detection

• Rotating Wall CompressionRotating Wall Compression

• FT-ICR Detection (optional)FT-ICR Detection (optional)

challenge : FT-ICR and rotating wall compression at the same time

m · D²

q² · R



Novel Amplifier DesignNovel 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)



Noise Chart of designed amplifierNoise Chart of designed amplifier

LC circuit at trap will show about 22nV/(Hz)1/2 @ 2MHzCin determined to 1.8pF strong decoupling 6:1 possiblePresumably low Tnoise~ 6K

Using NEC 3508 „super low noise“ HJ-FET (GaAs)



Rotating Wall CompressionRotating Wall Compression

T = 300K

T = 4.2K

non-linear filters reduce noise and allow FT-ICR at the same time

Low pass functionality, overruled at high amplitudes

Established 2008



Frequency and Amplitude responseFrequency and Amplitude response

Observations:General functionality verifiedClear Voltage Threshold as expectedOutput Excitation amplitudes somewhat too low Failure of diodes at Uin ~ 12Vpk or 240mApk => modifications will be tested coming weeks



Geometrical ArrangementGeometrical Arrangement



Another Idea: Charge Detector for AdjustmentAnother Idea: Charge Detector for Adjustment

Sensitive cryogenic charge amplifier on back side



Summary and OutlookSummary 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



Thanks a lot foryour attention.

Email: [email protected] www.stahl-electronics.com



Spare Slides:Spare Slides:



Examples of Coil-Design



Pickup-Elektrode

Pickup-Elektrode

x

y

Detection of Image Charges, FT-ICRDetection of Image Charges, FT-ICR



Pickup-Elektrode

Pickup-Elektrode

ion currentsignal

I

t


x

y



Pickup-Elektrode

Pickup-Elektrode

ion currentsignal

I


x

y

very smallsignal ~fA

Signal strength

D ~ distance of pickup electrodes



Pickup-Elektrode

Pickup-Elektrode

ion currentsignal

z

Voltage/Current Amplifier

Pe nning Tra p(c ro ss se c tio n)

ra d ia lly sp lit e le c tro d eslit

FFTFou rie r-Transfo rm - spectra l analyser

excited ion

m agnetic fie ld

low noiseAm p.

timetime-domain frequency-domain

I

frequency

dP /d fion current signal

mass spectrum

FFT

q/mspectrum

II

t f

x

y

very smallsignal ~fA


„FT-ICR“ Fourier-Transform Ion Cyclotron Resonance




• Method is non-destructive

• Many ion species can be detected at the same time

• Small sensitivity to space charges compared to TOFSmall sensitivity to space charges compared to TOF

• Useful over a very wide range of ion numbersUseful over a very wide range of ion numbers



FT-ICR CircuitryFT-ICR Circuitry



First HFirst H22OO++ Resonance: Resonance:



Shot Noise by Ions and ElectronsShot 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

Spectrap Electronics Evaluation of Cryogenic Components Begin 2009 Stefan Stahl measurements by...

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