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   Project Coordinator
   Prof. Theo Zouros
   Atomic & Molecular Physics
   Dept. of Physics
   Univ. of Crete, PO Box 2208,
  . GR-71003 Heraklion
   e-mail: tzouros@physics.uoc.gr

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Home > Work Packages > WP5 - Differentially pumped gas cell - design and construction
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Work Package 5: Differentially pumped gas cell - design and construction


Figure 1: Photos and drawings of the double differentially pumped gas cell. (3-2) Inner gas cell after carbon sprayed delrin with exit aperture (Ap3) supports shielded by metal nuts and plastic spacers.


Figure 2: Double differentially pumped gas cell schematic of: (Left) aperture arrangement and size, (Right) SIMION 3-D rendering after the change on Feb. 16, 2015.

Figure 3: Gas distribution supply center

Figure 4: Inside the gas cell showing the inner gas cell, the delrin support sprayed by graphite to supress charge-up and the ion exit side apertures.

Description of work package

Work Package



Month 7


Month 15



WP5: Differentially pumped gas cell - design and construction


Research Teams:

RT1, RT2, RT3

A low chamber (2-4Χ10-7 Torr) pressure with fully loaded (10-20 mTorr) target gas cell is crucial for obtaining high quality, low background electron spectra, particularly with position sensitive detection since it also reduces the dead time of the entire data acquisition This necessitates the use of a doubly differentially pumped gas cell with its own independent pumping system a concept first used with great success in Kansas.

5.1 Design of doubly differentially pumped gas cell: calls for a voltage floatable target gas cell enclosed in an outer cell and directly pumped by an independent turbo pump with μm XYZ alignment capabilities. Supporting the gas cell at the correct focusing distance is very important and will be studied in simulation using SIMION CPO software in conjunction with the input lens settings of the hemispherical analyzer. A 50-100 lt/s turbo pump with back up pump will have to be ordered and installed.

5.2 Gas cell construction and placement in collision chamber: Gas cell manifold, aperture assembly, pumping system and support will be built according to the design in the shop and positioned.

5.3 Connection to gas feed through and pressure stabilization unit: The gas pressure will be stabilized and monitored by a feedback system, typically a capacitive manometer, which will also have to be bought.

5.4 Gas cell alignment and support: involves the crucial optical alignment of the gas cell with the optical axis and is first performed in air with a telescope. Final micro adjustment to minimize electron background from slit edge scattering is performed by taking electron spectra with ion beam on target (WP8.1).


1 Report and part of BS, MS or PhD thesis

WP5: Table of Activities in progress

CompletedActivityTarget Date
Bought 8" 6-way (double) CF cross to be used for the gas cell chamber  
Jun 2013
Bought 560 lt/s Leybold turbopump to pump 6-way cross
Jun 2013
Bought 70 lt/s Leybold turbopump to pump gas cell
Jun 2013
Bought MKS Baratron gas cell pressure monitor and control system
Jun 2013
Modified Gas cell support to right distance in 6-way cross
Dec 2013
Tender for high purity target gases (H2, He, Ne, Ar) completed successfully
Jan 2014
Gas cell cleaned, tubed and prepared for use - HV wiring to vacuum feedthroughs modified - see lab book
Feb 2014
MKS Baratron manometer and gas control tested (problems encountered - units send to MKS Munich for testing and recalibration - returned)
Mar 2014
Gas cell final mounting and alignment
Mar 2014
Gas cell target gas supply center build
Mar 2014
Gas cell tested with Baratron under vacuum (problems encountered - units sent to MKS Munich for further testing and recalibration - returned)
Mar 2014
Baratron capacitive manometer returned repaired and recalibrated from MKS Munich and tested with He and H2
Jun 2014
Gas cell tested with ion beam for alignment and beam transmission
Jun 2014
Gas cell used in first projectile Auger electron measurements - first tests of differential pumping and spectrum background
Jul 2014
New translational stage build for Gas cell to allow for easy alignment
Aug 2014
New translational stage with Gas cell installed and aligned
Nov 2014
SIMION modeling of gas cell transmission in conjunction with 4-element lens voltages
Dec 2014
Correct tilt of gas cell and change to slightly larger diameter apertures to improve transmission (see New Gas cell )
Feb 2015
Final Report on operation of Gas cell ready - work package completed
Dec 2015

WP5: Deliverables

Additional related results:

  • M. Benis, Excel spreadsheet to calculate differential pumping for specific gas cell geometry
  • Gas cell system 3-D design (Aggelos Laoutaris) (SolidWorks eDRW file )
  • Gas cell ONLY 3-D design (Aggelos Laoutaris) Jan 2016 SolidWorks eDRW file )
  • New Gas cell schematic (16/02/2015)

WP5: People involved

  • Prof. Theo Zouros - MRG RT1 (UoC)
  • Giannis Madesis (PhD student) - GEC RT1 (UoC)
  • Dr. Tasos Lagoyannis - MRG RT2 (INP Demokritos)
  • Dr. Michalis Axiotis - GEC RT2 (INP Demokritos)
  • Prof. Theo Mertzimekis - GEC RT2
  • Dr. Tasos Dimitriou - GEC RT1 (UoC)
  • Aggelos Laoutaris - GEC RT1 (MS student)

WP5: Technical Notes

Work Package 5 ( continued): after end of THALIS grant (31/12/2015)

Figure 5: Cross section of gas cell showing distances (in mm) and new increased aperture diameters. As of January 2016.

Figure 6: Chamber pressure dependence on Target pressure

WP5: Table of Activities in progress

CompletedActivityTarget Date
Implementation of new larger apertures in gas cell as shown in Fig. 5
Jan 2016
First test with short duration beam time in Sept 2016. A record high beam intensity of 40nA in FC2 of 12 MeV C4+ was recorded. However, an unknown "shadow" was observed on the PSD image possibly related to some misalignment of the beam to the optics axis.
Sep 2016

Last Update: 29/12/16 19:22:57

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