COLUTRON TECH NOTES
Some frequently asked questions concerning the operation of Colutron ion beam equipment are discussed below.
I. ION BEAM PROBAGATION PROBLEMS
Unstable beam conditions: ion sources, ion gun systems, velocity filters
Equipment effected: ion sources, ion gun systems, velocity filters
Ion beam seems to be misaligned
Equipment effected: ion gun systems, velocity filters
II. ION SOURCE PROBLEMS
Unable to strike an arc with the source
Gaseous discharge in ion source gas inlet tube
Quartz ion source parts turn milky white and/or ion source ceramic parts cracked
III. MODEL CU-1 COOLING UNIT FAQ
Model CU-1 FAQ
Problem: Unstable beam condition
Cause: Floating ion source heat sink
Cause: Dirty ion optics (beam drift). Beam charge-up of electrodes from non-conductive beam deposits/contaminants. This is a common problem when using charge materials that oxidize when exposed to air, or when using diffusion pumps that coat the vacuum system with oil, or when operating the ion gun for extended lengths of time.
Cause: Floating electrodes.
Cause: Ion source gas leak will cause an unstable discharge.
Cause: Missing 100-ohm power resistor in series with anode connection.
Remedy: Make sure that a 100-ohm, 50 watt resistor is connected between the anode supply and anode. This resistor is used to stabilize the ion beam by inductively damping plasma oscillations within the discharge.
Cause: Anode and filament power supplies are being operated in current control.
Remedy: Make sure that the ion source power supplies are VOLTAGE regulated.
Problem: Beam alignment problems
Cause: With the velocity filter magnet and electric field supplies turned off, the ion beam does not propagate on axis to a Faraday cup or other measurement device down stream. This is due to the residual magnetic field of the velocity filter.
Cause: Floating electrodes
Cause: Dirty electrodes
Problem: Unable to strike an arc with the ion source
Possible Causes: Filament voltage and/or anode voltage too low. Anode not connected to the anode contact wire. Inadequate gas or solid charge present. Ion source leaking gas.
Problem: Gaseous discharge in ion source gas inlet tube
Cause: Ion source gas inlet valve not floating, but at ground potential resulting in an electrical discharge due to rarefied gas. Ion source gas pressure could also be too high.
Problem: Quartz ion source parts turn milky white and/or ion source ceramic parts cracked.
Cause: Ion source is operated at too high of temperature.
Cause: Insufficient cooling.
Remedy:Make sure that the ion source heat sink output coolant temperature does not exceed 100° F (40° C). Ensure that the heat sink coolant rate is at least 0.5 liter/minute. Also, adjust the ion source insertion depth on the ion source receptacle flange so that the ion source cap just barely (1/2mm-1mm) comes into contact with the end of the heat sink. Do not force ion source into heat sink. Ion source cooling is mainly accomplished by thermal contact of the cap and heat sink. The 1/2mm gap allows for expansion of parts.
Filament frequently asked questions
Question:My filaments do not seem to last very long?
Question: What are the different applications for the two types of filaments offered by Colutron?
Answer: The PN-120 (20) mil filaments are used when a greater source temperature and/or maximum beam current is desired. For some reactive gasses such as oxygen and chlorine, it is advisable to use a PN-115 (15 mil) filament because the source plasma temperature will be decreased. This reduces damage to ion source parts from the hot reactive gasses. The 15 mil filaments are also used when a smaller beam current is required.
Question: What is the best filament to use for oxygen ions?
Answer: The PN-115 (15) mil filaments are used when a cooler plasma is required. This is important for generating oxygen ions. The best filament material is thoriated iridium wire. This is currently unavailable from Colutron, but we are working to add this filament to our product line.
Model CU-1 Cooling System frequently asked questions
Question: Where is the expansion or metering valve?
Answer: The Colutron model CU-1 (HFC-134a) cooling system does not use a metering valve. The unit does not operate as a standard air conditioning system, but is used to remove heat from the refrigerant through the unit's condensing coils.The CU-1 compressor, cycles the refrigerant in a liquid and gas mix through the ion source heatsink and velocity filter magnet coils. When the hot refrigerant (80-100
Question: The refrigerant seems warm or hot to the touch. Is something wrong?
Answer: The normal coolant temperature with the ion source operating is 80-100
Question: The cooling unit switches off after running for a short time. What's happening?
Answer: The cooling unit pressure switch is set to shut the compressor off if the coolant pressure exceeds 150 pounds/square inch (PSI). Make sure that your pressure switch is set at 150 PSI. If the pressure switch is set for 150 PSI and the cooling unit still shuts off, the cooling unit may have been overfilled with refrigerant. The normal charge is 2 pounds HFC-134a (R-12 on older models). Also, if the lab temperature is hot (90-100
Question: I am having problems charging the cooling unit. What is wrong? How do I fill 2 pounds of refrigerant?
Answer: Make sure that the compressor is running, and open the inlet valve on the suction side of the compressor. To fill 2 pounds, put the refrigerant tank on a weight scale and fill until tank weighs 2 pounds less.
Question:I have heard that the compressor will be damaged if it compresses liquid refrigerant. Is this true?
Question: I have an old Colutron cooling unit that uses the now banned R-12. Can I use the new ozone safe HFC-134a in my unit?
Answer: No. The old R-12 units use a mineral-based oil, and the new HFC-134a units use a poly-ester-ether based oil. They are non-compatible. It is possible however to retrofit the older units by completely draining the mineral oil and adding the poly-ester-ether oil. This process is difficult, since ALL the mineral oil must be removed. The compressor label should have information about the amount of oil required.
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