Residual Gas Analyzer FAQ

Frequently Asked Questions

 What are the advantages of using an Extorr over just a total pressure gauge?

Most vacuum systems are outfitted with a total pressure measurement device such as an ion gauge, Penning gauge or Pirani gauge. An Extorr on a vacuum system is able to measure pressures from atmosphere to Ultra High Vacuum with its built-in Pirani and Ion gauge.  All of these gauges will indicate how much total gas remains in the vacuum system.  When the required level of vacuum can not be reached, other total pressure gauges can give no further information as to why.  Unlike the other gauges, Extorr’s residual gas analyzer (RGA) quadrupole mass spectrometer can identify the problem in seconds. The failure to achieve the desired vacuum level may be due to an air leak, hydrocarbon contamination, excess water vapor or maybe the presence of a cleaning solvent. The RGA will identify the problem gases and thereby rapidly pinpoint the steps required to solve the problem.  more about the B/A, pirani

 What are the advantages of using an Extorr over just an ordinary RGA?

Having the total pressure measurement capability, of the built-in Pirani and ion gauge, clearly separates the Extorr from the other RGAs.  Not only does the Extorr offer more vacuum measurement capabilities, it also packs these capabilities into the smallest package.  The probe is self supporting and does not require a nipple for support.  This allows the electronics to extend a mere six inches from the vacuum access port.   Even with the extra pressure gauges and size advantage, the Extorr RGA makes no compromise in performance.  With high stability, sensitivity, operational flexibility, and modern software, the Extorr systems are truly the next generation RGA.

 In what pressure range does the Extorr work?

The Extorr systems are really three vacuum measuring devices all housed on a single probe.  The Useful range of the Pirani gauge section is from atmospheric pressure to 10-2 torr.  At 10-2 torr the ion gauge filament starts to turn on with a reduced electron current.  The ion gauge operates at this reduced emission until 10-4 torr.  At this point the filament turns fully on and quadrupole partial pressure readings become available.  The total pressure is still determined by the ion gauge all the way down to about 10-9 torr where the x-ray limit of the gauge is approached.  Partial pressures give useful qualitative information at pressures between 10-4 and 10-5 torr and become more quantitative all the way to partial pressure readings in the 10-12 torr range.With the addition of the optional multiplier, some partial pressures may be observed to below 10-14 torr.

 Can I apply power, at atmospheric pressure, to the Extorr Electronics (CCU) when it is plugged into the probe?

Sure, the unit is intended to start measuring pressure at atmosphere using the built-in Pirani gauge.  The constant checks of total pressure make the Extorr virtually indestructible.  The electronics may be operated at any pressure, either connected to the probe or not.  No harm will come to the probe or the electronics.

 I need to make measurements of the partial pressures of a gas at atmospheric pressure.  Can I use the XT instrument for this purpose?

The Extorr RGA (partial pressure) mode requires a UHV vacuum system for operation.  A small vacuum system pumped by a turbopump would be able to accomplish this.  The nature of the gas to be sampled, and what you would like to find out about this gas, will determine the type of gas inlet you will need for this system.  A great deal may be learned by using a simple capillary, aperture, or leak valve. 

 Where are the Extorr systems Manufactured?

Extorr does their manufacturing in New Kensington, PA, just a few miles up the Allegheny River, from Pittsburgh, in Western Pennsylvania.

 Do I need an electron multiplier?

The base model XT systems have a Faraday cup detector for the partial pressure measurements. The base model measures only the current from the actual ions which are separated by the quadrupole. The models designated by the letter M at the end of their name, have a multiplier detection system as well as the Faraday cup. In these models, an amplified electron current stemming from individual ion collisions with a surface, is measured. A current gain, which may be on the order of a million, allows for a huge increase in possible sweep speed to achieve a given signal to noise ratio. The same signal multiplication extends peak detection by a factor of 1000 or even more.

 Is the XT100 for $3450, the complete package?

Yes, the XT100 is complete with probe, electronics and software.  All that is required is a vacuum system, with a 2 ¾ inch Conflat port, in which to place the probe.  A Windows 2000, XP, 7, 8, or 10 computer with a USB or an RS 232 serial port is required to run the software.

 What sort of warranty comes with the unit?

Extorr extends a full one year parts and labor warranty for its XT systems. Of course the filaments and ionizer are considered consumables and cannot be warranted. Misuse of the probe will not be covered, with respect to mechanical abuse or contamination.

 Does the Extorr work in conjunction with other data acquisition programs?

Automation with data acquisition systems is available in that the Extorr VacuumPlus software follows the Windows standards. Data output and operational parameters may be changed automatically by user written programs in common programming languages and scripts. Extorr software supports text out, image out, as well as the XML data structure. Both configuration files and data files are in the XML format. VacuumPlus has a streaming XML data port.

 Does the Extorr supply LabView drivers.

Currently, no LabView drivers are available for the Extorr.  It is our understanding that the latest LabView Software supports an XML data structure.  The Extorr software, VacuumPlus, completely supports the XML data format.  Both configuration files and data files are in the XML format.  Vacuum plus has a streaming XML data port.  For now, Extorr suggests, that the streaming XML data transfer is the best way to deal with LabView.

 What are the differences between the XT100, XT200, and the XT300?

The basic difference is that the XT 100 goes up to mass 100 amu, the XT200 goes up to 200 amu and the XT300 goes to 300 amu.  All units start below mass 1.  With each increase in mass range, there is an increase in quadrupole quality and electronics power output.  The current prices are such that each increase in mass range produces a $1000 increase in price. 

 Does Extorr have an analog output?

No. To avoid problems with electrical interference, ground loops, and noise, Extorr does not place an analog output on the CCU.  Digital to analog computer cards are common and may be driven by the XML output from the software. 

 Does the Pirani portion of the ion source require any calibration?

The Pirani gauge is factory calibrated but may be placed through a two point calibration for occasional recalibration.  The user pushes a software button when the system is at atmospheric pressure and a second button when the pressure is below 10-3 torr.  The calibration curve is then fit to those two points.

 How long do Extorr filaments last?

The Extorr filaments are protected against overpressure by the ion gauge function of the probe.  The ion gauge pressure is read at all times whenever the Pirani gauge indicates a low enough pressure.  Any harmful pressure excursion will result in the filaments being turned off.  The filaments are thoria coated iridium.  The thoria allows for a high electron emission without ever approaching the melting temperature of iridium.  When operated in a benign vacuum with pressures always below 10-7 torr, the filament is expected to last far over a year.  After an extended period of operation, the filament may experience evaporation, become thinner, and eventually fail.  Accelerated failure could be brought on by heavy use on corrosive gases at pressures in the 10-4 torr region and above.  Overuse of the degas function may also lead to a decreased filament lifetime.

 How do you use the degas function?

Gases absorb on all surfaces including the ion source surfaces.  Over time, these surfaces desorb these gases, increasing the background spectrum of the RGA.  The degas function sprays high energy electrons from the source filament which then heat and degas the surfaces of the ionizer.  The filament in this mode runs hotter than usual so it is recommended to degas for only about five minutes at a time to avoid premature failure of the filament.

 How easy is it to replace the filament?

Once the analyzer has been taken out of the vacuum system, the filament may be rapidly exchanged. A clean pair of needle nose pliers and the allen wrench provided with the new Extorr filament are all the tools required.

 Can the software support more than one Extorr unit?

Yes the software supports as many Extorr units as there are serial ports, both real and virtual, on your computer.

 Can a Faraday cup unit be upgraded to a multiplier detection system in the Field?

Yes, a multiplier detector kit, MULTKIT, is available to convert any XT(N)00 into an XT(N)00M. The multiplier is plugged into the probe and a high voltage module is plugged into the electronics box. No special tools are required except proper vacuum practices (clean gloves) should be employed when handling the multiplier.

 Other RGAs have a 5 inch Conflat nipple on their probes.  Can you supply one of these?

Yes. Unlike some other RGAs, the Extorr probe is self supporting and does not require such a nipple.  At the customer’s option, the probe may extend into the vacuum system or not.  For those that require a less intrusive ionizer position, a five inch long Conflat nipple is available from Extorr.