The XIA Models DP-03 differential pumps provide a cost effective, windowless, direct, line-of-sight transition between an ultra-high vacuum (UHV) region (< 1 x 10-9 Torr) and a high vacuum (HV) region (< 1 x 10-4 Torr).

Data sheet
(PDF format, 299KB, April 14, 2021)

User’s Manual

Mechanical Drawing in pdf format (34 KB)


  • Windowless HV to UHV vacuum isolation
  • Five orders Pressure Isolation
  • Clear through aperture to 10 mm H x 14 mm W
  • Standard form only 34″ long overall
  • Custom versions too
  • NEW! Line of sight pumping available

General Description

Differential pumps traditionally consist of a series of pumps separated from each other and from the UHV region by flow restricting throttles. The DP-03 adheres to this arrangement, consisting of a pair of throttles separated by an active pumping region. An adapter nipple on one end facilitates connection to HV, while an adapter cross on the other end makes the connection to the UHV system as well as providing ports for pressure monitoring, viewing, and attaching the user supplied secondary pump which completes the system. Innovative in design, the DP series is able to provide quite large through apertures while keeping the overall pump length short by placing distributed pumping close to the line of sight through the differential pump. This enhances effective pumping speed by up to 10 compared to conventional ion pumps of similar dimension. For most applications only a single DP-03 stage and a 30- 60 l/sec exit pump will be required. DPs are easy to configure to specific applications, allowing their owners to optimize the tradeoff between through aperture dimensions and the amount of isolation provided. This is accomplished by adjusting the dimensions of the two throttles and by selecting the pumping speed of the user supplied exit pump. Throttle aperture dimensions are specified at time of order, but can easily be removed and altered later. Further details are provided below in the section on performance.

New: Molecule “Line of Sight Pumping”. All models now contain an XIA patented innovation which passes the line of sight directly through the active pumping region of a Penning style ion pump. The Penning electrons trapped by the magnetic field in the ion pump’s active pumping region have a substantial cross section for “straight through” molecules and are able to remove the vast majority of them. Tests on a “Line of Sight Pumping” DP, using an RGA sensitive to 10-14 Torr, were unable to detect any straight through N2 beam on the UHV side when the HV side was at 10-5 Torr. Further, the new design also offers better pumping speed, so that the model Eqn. 1 in the data sheet should be regarded as a upper limit on performance.


X-ray Lithography & Microscopy 
Simplifies the design of alignment and exposure equipment and allows window free expose of resist materials at 10-6 Torr.

Thin Window Elimination 
Removes the operating complexities associated with fragile windows while transmitting full intensity in the soft x-ray range. Also a possible solution in situations where high power loading on thin windows is a problem.

UHV Incompatible Materials
Now surface science or soft x-ray experiments can be carried out on materials whose vapor pressures exceed 10-9 Torr. With an additional stage of pumping the direct study of sputtering and low pressure CVD are possible.

Faster Sample Chamber Cycling
If UHV conditions are not actually a necessity for your experiment, install a DP-03 and operate your sample chamber at 10-6 Torr. The need for bakeouts will be eliminated and cycle times will drop from days to minutes.

Remove Unwanted UHV Restrictions
Complex precision mechanical devices such as monochromators may be an order of magnitude more expensive at 10-9 Torr than they are at 10-6 Torr. In many cases it will be cost effective to isolate such devices from both the storage ring and the experiment, using two DP-03s in order to employ 106 fabrication technology.


The following specifications are for Standard DP Models only. Performance specifications for custom models may vary and will be established on a quotation basis.

Performance specifications
Following an adequate bakeout cycle conducted according to generally agreed upon good vacuum practice and tested as described in the User’s Manual, a DP will achieve the following:

BACKGROUND PRESSURE: 3 x 10-10 Torr or better.
N2 PRESSURE ISOLATION: within a factor of two of the values predicted by Equation 1 in the data sheet.

  • Overall dimensions
    (Please see the pdf schematic diagram)
  • Throttle dimensions
    LENGTH: 6″ (15 cm)
    APERTURE: specified at time of order, up to 10 mm high by 14 mm wide.
  • High voltage connection
    Varian 954-5143 or equivalent.
  • Materials:
    BODY: Type 304 Stainless Steel
    PUMP: Type 304 Stainless Steel
    ADAPTER CROSS & NIPPLE: 304 Stainless Steel.
    THROTTLE TUBE INSERTS: 6061 Aluminum alloy.
    MAGNET: Ferrite.
  • Connection flanges
    ADAPTER NIPPLE TO HV: 4.5″ CF.flange.
    ADAPTER CROSS: 4.5″ CF flange to UHV; two 4.5″ CF flanges for pump connections and two 2.75″ CF flanges for pressure gauges, viewports, etc.
  • Mounting
    4 HOLE, NON-KINEMATIC DESIGN: 4 bolt holes to attach the pump to the mounting structure of the customer’s design.
  • Alignment aids
    TOOLING BALL SOCKETS: 0.250″, 4 provided.
  • High voltage supply & cable
    BOTH USER SUPPLIED: -5.2 kV required. We recommend the Varian Midivac 929-6000 Negative HV Card supply and 929-0770 HV bakeable cable or equivalents.
  • Pump Life
    35,000 HOURS MINIMUM with inlet P 1 £ 1 x 10 -6 Torr
    and increase as throttle conductances decrease.
  • Temperature Limits
    PUMP: 375° C. MAGNET: 150°C.

Standard Designs

Presently there is a single “standard” design available. Many simple design changes, including lengths of spooling, flange dimensions and even pump rotation about the line of sight, can be adjusted without requiring a “custom” design. Please contact the factory with your requirements.

  • DP-03: Horizontal design, 34″ overall length, 4-point non-kinematic mounting. Includes patented XIA “Line of Sight Pumping”. Throttle dimensions up to 45 mm horizontal by 20 mm vertical.

Custom Designs:

XIA differential pumps can be customized in many ways to accommodate the specific requirements of different applications. For example, pumps with magnetic shields have been built to accommodate operation in close proximity to electron spectrometers. Customers are encouraged to contact XIA with their needs. The basic DP-03 design is intended for laboratory sources or bending magnet beam lines. Details concerning its connecting flanges, mounting geometry, additional ports, etc. are simple and not expensive to modify. For wiggler or undulator applications the throttles will require modification to avoid direct beam strike and introduce cooling. XIA can either contract to design these modifications or work with your engineers to develop an acceptable design. Even more extreme modifications can be considered for applications we have not yet imagined. We look forward to hearing your ideas.

Ordering Information

  • Warranty:
    One year
  • Delivery: 
    STANDARD MODEL DP-03:  12 weeks ARO.
    CUSTOM DESIGNS: As per quotation.
  • Purchasing Contact