Miniature Knudsen Cell - Molecular Effusion Source

NEW PRODUCT!

This miniature K-cell from SciCam provides a stable high temperature furnace for the controlled deposition of a wide range of materials. This is the ideal tool for reproducibly depositing small areas of thin films of material with coverages from monolayers to continuous film. For maximum versatility the furnace is fitted with easily removable crucibles (liners) made of PBN or Alumina to suit the deposition material. The liners are are fitted with removable apertures which define and limit the output beam. The modular 'cartridge' design means that all parts are easily replaceable so that a new furnace or liner may be inserted to accommodate a change of materials or for routine maintenance.

Features of the miniature K-Cell

  • Intrinsically stable evaporation rate
  • Operates up to 1500 degs for a wide range of materials.
  • Small size fits on a 70 mm OD CF flange.
  • Three K-Cells fit an 6 " OD flange for co-deposition
  • Quick change liners make it easy to change materials
  • Modular 'cartridge' design for easy maintenance and operation
  • Custom lengths available
  • Proven design hundreds already in use.

Operating Principle of the K-Cell

The SciCam Knudsen cell utilizes the principle of molecular effusion ( demonstrated by Knudsen in 1909). . The material to be deposited is heated to provide a suitable vapor pressure in an isothermal enclosure. Molecular effusion from an aperture in the end of the cell gives rise to a cosine intensity distribution. The deposition rate is extremely stable being determined by the temperature of the furnace which is accurately controlled with a PID controller.

Furnace

Furnace & liner

The graphite furnace of the cell is designed as a removable cartridge which contains the crucible, heater element and heat shields. The heater filament is a tantalum foil element which is isolated with PBN shields. The temperature of the furnace is monitored by a thermocouple which is carefully placed in the graphite in order to accurately reflect the internal temperature of the furnace. The crucible can be changed by the user and is available in PBN and alumina.

Power Supply and Temperature Control

K-Cell controllerThe power supply/controller is three term PID controller which takes account of the need to regulate the power to the heater depending on the filament temperature. The set temperature is displayed on an LCD panel.

Specifications of K-Cell and Controller

Max operating temperature 1500 degs. C  
Heating method Tantalum foil  
Bakeout temperature to 250 degs. C  
Typical Power at 1500 degs.C 125 W  
Apertures 1 mm supplied optional 1.5, 2.0, 2.5, & 3.0 mm  
Crucibles ( Liners ) Graphite Crucible (liner) Pyrolytic Boron Nitride
Density 1.82 g/cc 2.15 g/cc
Open Porosity 8% 0%
Capacity 0.5 cc 0.4 cc
Note that nitrogen dissociates from PBN at high temperature. Typical dissociation pressures are 2.4 x10E-10 at 1200 K and 4.1x10 E-3 at 1800 K
Cooling Integral water or LN2  
Water flow required 0.25 l/min  
Thermocouples    
Standard - temp range 500 - 1500 C Type W3 W-3%Re/W-25%Re
Optional - temp range 200 - 1200 C Type R Pt/Pt - 13% Rh
Temperature Controller Three term - PID type  
Temp control stability =/- 2 degs. C or 0.3%  
Temp readout and set point digital display  
Power supply weight 8.5 Kg  
Power supply dimensions 19 ' x 2U (19" x 13.25" x 3.5" ) 482 mm x 336 mm x 88 mm

Ordering Information

Item Part Number
1) K- Cell Body & Shutter KC3-Body
2) Graphite Furnace W-3%Re/W-25% Re KC3-GRA-W3
3) Graphite Furnace with Pt/Pt - 13% Rh KC3-GRA-R
4) PBN liners and end caps KC3-PBN
5) Alumina liner and end caps KC3-ALU
6) Spare PBN end caps (2) KC3 PBN-CAP
7) Spare Graphite end cap (1) KC3-GRA-CAP
8) Spare Heat Shield Aperture KC3-HSA
9) Spare K-cell multipin socket KC3-SKT
10) Control Unit (leads included) 250 PC
11) Connection Leads (for own power supply) KC3 - SKT
Note a complete unit comprises a Body and Shutter(1) + a furnace( 2 or 3) + a liner and end caps ( 4 or 5)+ a controller with cables (10)
 
Topac Inc 231 CJC Highway, Cohasset MA 02025 USA
Tel: 781 740 8778 Fax: 781 740 8779 e-mail: sales@topac.com

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