Download Evaluation of Cryogenic Components Begin 2009

Spectrap Electronics
Evaluation of Cryogenic Components Begin 2009
Stefan Stahl
measurements by
Stefan Stahl & Zoran Angelkovic
Spectrap Evaluation of Cryogenic Components
Preface: main objectives
• Resistive Cooling of captured ions to T = 4.2K and ion detection
t=
m · D²
q² · R
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
Spectrap Collaboration Meeting, April 2, 2009
Spectrap Evaluation of Cryogenic Components
Novel Amplifier Design
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)
• FET with low input capacitance => low heating of
LC circuit
• Additional cascode circuitry further lowers CIN
Spectrap Collaboration Meeting, April 2, 2009
Spectrap Evaluation of Cryogenic Components
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
Spectrap Collaboration Meeting, April 2, 2009
Spectrap Evaluation of Cryogenic Components
Rotating Wall Compression
T = 300K
Established 2008
T = 4.2K
non-linear filters reduce noise and allow
FT-ICR at the same time
Low pass functionality, overruled at high amplitudes
Spectrap Collaboration Meeting, April 2, 2009
Spectrap Evaluation of Cryogenic Components
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
Spectrap Collaboration Meeting, April 2, 2009
Spectrap Evaluation of Cryogenic Components
Geometrical Arrangement
Spectrap Collaboration Meeting, April 2, 2009
Spectrap Evaluation of Cryogenic Components
Another Idea: Charge Detector for Adjustment
Sensitive cryogenic
charge amplifier
on back side
Spectrap Collaboration Meeting, April 2, 2009
Spectrap Evaluation of Cryogenic Components
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
Spectrap Collaboration Meeting, April 2, 2009
Spectrap Evaluation of Cryogenic Components
Thanks a lot for
your attention.
Email: [email protected]
www.stahl-electronics.com
Spectrap Collaboration Meeting, April 2, 2009
Spectrap Evaluation of Cryogenic Components
Spare Slides:
Spectrap Collaboration Meeting, April 2, 2009
Spectrap Evaluation of Cryogenic Components
Examples of Coil-Design
Spectrap Collaboration Meeting, April 2, 2009
Spectrap Evaluation of Cryogenic Components
Detection of Image Charges, FT-ICR
Pickup-Elektrode
x
y
Pickup-Elektrode
Spectrap Collaboration Meeting, April 2, 2009
Spectrap Evaluation of Cryogenic Components
Detection of Image Charges, FT-ICR
Pickup-Elektrode
ion current
signal
x
I
y
t
Pickup-Elektrode
Spectrap Collaboration Meeting, April 2, 2009
Spectrap Evaluation of Cryogenic Components
Detection of Image Charges, FT-ICR
Pickup-Elektrode
ion current
signal
x
I
y
Pickup-Elektrode
very small
signal ~fA
Signal strength
D ~ distance of pickup electrodes
Spectrap Collaboration Meeting, April 2, 2009
p
Spectrap Evaluation of Cryogenic Components
low noise
Detection of Image
Charges,
Amp.
Pickup-Elektrode
ion current
signal
x
I
y
ion current
signal
I
ted ion
FFT
Fourier-TransformFT-ICR
spectral analyser
I
dP/df
q/m
spectrum
mass spectrum
FFT
slit
radially split electrode
Pickup-Elektrode
very small
signal ~fA
t
time
time-domain
„FT-ICR“
f
freque
frequency-domain
Fourier-Transform Ion Cyclotron Resonance
Spectrap Collaboration Meeting, April 2, 2009
Spectrap Evaluation of Cryogenic Components
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
Spectrap Collaboration Meeting, April 2, 2009
Spectrap Evaluation of Cryogenic Components
FT-ICR Circuitry
Spectrap Collaboration Meeting, April 2, 2009
Spectrap Evaluation of Cryogenic Components
First H2O+ Resonance:
Spectrap Collaboration Meeting, April 2, 2009
Spectrap Evaluation of Cryogenic Components
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
Spectrap Collaboration Meeting, April 2, 2009
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