One can operate the VM Series Spectrometers by pumping through the entrance slit thus eliminating the cost of a pumping system for observing a source of VUV radiation in a lab system that has a pumping station. This can be done using the 2.75 inch CF attached to the entrance slit. One can also isolate the spectrometer with a window and pump from the back of the main housing. It is also possible to purge the spectrometer with Nitrogen, Argon or Helium if the window approach is used.
A pumping station we have used for many of our systems is the Pfeiffer HiCube™ ECO Dry Pumping Station available in the US for $6,995 from Kurt Lesker and others. We have not found any less expensive systems that include high vacuum pump, dry backing pump and electronics. It is entirely suitable for high vacuum work in the VUV with Resonance monochromators, spectrometers and light sources.
A minimal system for operating the VM series spectrometers would include a vacuum gauge for the 1000 mb to 10-9 mb range like the KJLC 392 Series Wide-Range Combination Gauges which costs $1,033 from Kurt Lesker and vacuum connections. A typical setup is shown below:
The following VUV spectrum was created with the Resonance EUV flow lamp and VM92 with the VMCCDPh CCD detector.
Dec 10, 2016 Topic: target distance
It is specified that the maximum distance from target is 12" (which is too far for us) and the minimum is 4". Is this distance adjustable by us or does it need to be set in factory?
The distance can be adjusted by yourself. These lamps are made to order, so a shorter tube length can be created if needed.
In the quote, a 2.75" C/F flange is also specified for this lamp. Could you also tell me the meaning of this? If it is to fit with our vacuum chamber, a 6" C/F flange is required.
And finally, we would like to know how the beam shape looks like. Is this radiation constant within the 45 degrees cone you describe?
As you can see from the figures below the intensity drops as the axial angle increases. This fall off is determined by the geometry of the lamp. The D2 lamp has a narrower angle of illumination because the plasma is more condensed away from the window. The Kr is wider because the plasma extends up to the window.
Dec 16, 2016 Topic: Eye Safety
Because we want to purchase one of your Krypton lamp, we also would like to purchase VUV protection glasses for safety purposes but they seem to be difficult to find.
By any chance, do you have the contact of a company that can provide this kind of equipment?
Our Kr lamps have VUV emission at 116 and 124 nm and visible emission above 420 nm with little else. The 116 and 124 nm light is absorbed by air and does not pose an eye hazard. The radiation >420 is weak in comparison to room lighting and also is well below any eye hazard thresholds. The light from the lamps is incoherent and thus is not a high intensity beam like a laser so the usual concerns with lasers are not relevant.
Additionally the glass in normal glasses or the plastic in safety glasses will absorb the VUV even more effectively than air so if regulations are a concern any safety glasses will work.
Jan. 18, 2016 Topic: Intensity of Kr and Xe lamps
Preamble: A simple test for VUV output is to sniff the front of the lamp while it is operational. The power outputs are on the order of milliwatts which is enough to create an ozone smell. Eye protection should be worn but the VUV output is completely absorbed in a few mm of air so there is little danger.
1) I tried the Ozone “experiment” and actually I feel that I smell more ozone (smell like bleach, pool) with the two lamps that aren’t actually working (D2Ar and XeE lamps) compared to the other lamps (KrL and XeL lamps).
If what you smell is Ozone the lamps are emitting VUV. This smell should not be there when the lamps show no plasma (e. g. power off). If it is there may be some breakdown in the electronics which would smell like Ozone.
2) Is there another way to test the functioning of the lamps?
If you can take the VUV detector off of your vacuum system try moving the lamp from 10 mm (away from the lamp window) to less than 1 mm while observing the current. If you see a big increase the lamp is emitting VUV.
Another test would be to position the lamp 2 to 5 mm from the window and direct a stream of Argon or Nitrogen between the lamp and the detector. The only way the signal can increase would be with VUV.
3) Did you receive the pictures of the lamps with the serial numbers?
Yes and one lamp was built in 1990 and the other in 1998.
4) I also read that a problem with VUV light sources is that the need to be re-calibrated with time since their spectra may undergo variations due to changes in gas composition and/or transparency of the windows. Do you think it could be possible with the lamps?
It is possible that the lamp bulbs may have changed since the oldest is 27 years old. I have no idea how much they were used although they were full intensity in 2000 when we re-calibrated them. See the data below:
5) Is there a way that you could check that?
Yes, if you send them back we can re-bulb or re-calibrate the lamps. Do you wish a quote?
Before you send them back could run the lamps with the power supplies provided and take pictures with a digital camera at several different exposure levels so we can get an idea of the quality of the gas
Jan. 20, 2017
1) Can you give me any information about the expected lifetime of this source?
MInimum of 300 hours for the bulb.
2) We would potentially be interested in modulating the output. Can you tell me anything about the nature of the modulation? What is maximum modulation speed and what is the maximum extinction of the radiation when a modulation is applied?
All lamps systems now come with modulation. The lamp switches off when a 3 to 6V signal is applied to the modulation input. Modulation is usually used in a phase sensitive detector in order to remove background at other frequencies. We usually use 100 to 200 hz although a hydrogen lamp can modulate up to 1 kHz.
3) It says that it can be operated as an optically thin source which presumably means it will only be emitting Lyman alpha radiation. However, can you quantify the amount of other wavelengths present? I am assuming there will always be a small amount of radiation at longer wavelengths.
Yes we can measure the total out of band radiation.
4) I read that the device has a NIST traceable calibration. What sort of accuracy can we expect?
Approximately 10 % accuracy
5) Do you see any problem with the device operating in 100 Gauss magnetic fields?
Wow. I really do not know. Is it possible to shield with Mu metal?
6) Will any support electronics be required that are not mentioned on the quotation?
No. You can use the input modulation signal to synchronize.
Jan 20, 2017
1) You said the bulb has a lifetime of 300 hours. If the bulb burns out, can it be replaced or does the entire unit need to be replaced? If the former, how much would a replacement bulb cost?
Replacement bulb cost is approximately 500 and you can replace it, although we can also do it and re-calibrate in the unit.
2) You specified that you can measure the out of band radiation. But can you give me some idea now of how much power will be out of band? My main concern is that we may need to use a detector which has some sensitivity at visible wavelengths (down by a few orders of magnitude probably). If the out of band radiation is comparable to the Lyman alpha (or larger) then we may have a calibration issue. If the total out of band radiation is 1 order of magnitude less than the Lyman alpha power then I think there is no issue. Does that seem like a reasonable assumption?
Can you tell me what detector you will use? Typically we see > 60% absorption of Lyman Alpha with a filament driven H atom source with a CsI diode sensitive to from 113 to 170 nm. This includes out of band radiation plus imperfect overlap between lamp ly alpha and H atoms at 350 to 400 K.
3) Probably it will be possible to shield the magnetic fields. I am not concerned about about the electronics in that level of magnetic field. There are lots of electronic devices within that area. However, it may be that the discharge has some issues. In any case, we will work around that.
There might be some Zeeman effect and Hall currents which may have an effect on the exciter. However Kilogauss is usually the threshold for Zeeman.
Jan. 23, 2017 Topic: Multiple wavelength lamps for UHV applications for material testing
We are looking to add a VUV source to our surface science setup. We would like to enquire about your electrodeless atomic line light sources. To begin with we want to look at Ly-alpha, and so need a hydrogen lamp, but it is possible that we would like to branch out and look at other wavelength regions.
1 Are your lamps compatible with different types of gases, or are they made specifically for one?
There are three options to change the output of a single lamp:
a. Purchase a lamp with replacement bulb with other gases. This is most easily done with Kr (116.5 nm and 123.6 nm) and Xe 147 nm. However you would have to remove the lamp from the vacuum chamber to change the bulbs.
Purchase a hydrogen lamp which is calibrated to run at different internal heater temperatures. At low heater temperatures the lamp output is primarily Lyman Alpha and at higher temperatures the main output is between 130 and 170 n with a continuum between 170 and 300 nm. Refer to pages 9 and 10 in the following link
c. Purchase a flow lamp with a magnesium Fluoride window. With an Argon flow you will get a peak around 129 nm (113 to 145 nm). With Krypton you will get the 116.5 nm and 123.6 hm. And with Xenon you will get the 147 nm. This is the lowest up-front cost but it would require a pumping station and gas supplies which would likely make the start up costs higher than the a. or b. options.
2. Also, do all three types listed on your website fit standard CF flanges, and are they UHV compatible?
Yes, we do have CF flanges but the lamps usually have viton O ring seals between the lamp tubes and metal bodies. People have used them on systems below 10-7 torr and we have operated them in the 10-8 torr range. Also one system we made with similar seals operated down to 2 x 10-10 torr. However viton is technically not UHV.
3. Is it possible to control the wavelength output on any of your sources, to get both a broadband and narrowband emission?
Yes that can be done with the hydrogen light source.
4. Finally, we would like to ask for a quote on any of the series -L, -LQD12, and -LHP compatible with CF mounting on a UHV system.
See above. It would be helpful if you could tell us your vacuum requirement in torr and or max allowable helium leak rate before I quote. If viton is not allowed we might make a re-entrant tube with a UHV window flange which can be purged.
I am very interested in lamps with high fluences (between 50 and 100 mW/cm2) at wavelengths ~250 nm, and possibly as low as possible fluences around 300 nm.
I saw on your website that you have Xe Flash Lamps and LED kits. What do you think could best achieve the experimental criteria I just mentioned?
Could you also mention what kind of equipment would be needed to run these lamps and include all of them in two quotes: one quote concerning Xe Flash Lamp and the other about the LED kit at 250 nm?
Off hand I'd say the most cost effective way to achieve those fluences is a low pressure mercury lamp in a reflective enclosure. Those fluence levels are way outside of the power levels of the 250 nm LEDs which are much much less efficient than LEDs at 390 nm. The Xenon lamp would also work but it is not as cost effective.
The ratio of 254 to 300 nm radiation would be on the order of 50 to 1 without filtering the 254. The emission is primarily concentrated in specific lines so a narrow band filter between the lines might be used to reduce interference if that was the objective.
We built a chip treatment system for 30 to 70 samples about 1 cm 2 (with intensity levels of 200 mW/cm2).
Q1: Can you give me an idea of the size and shape of the target surfaces and if you need to expose them or measure them?
This system is cooled by attached fans and runs off of normal AC power with a total power of 500 W. The sample exposure rack slides into the tube.
Variations of this system could be used to look at fluorescence and or phosphorescence.
Optical filters on the spectrometer that cut off below 2xx nm would reduce the interference from the lamp.