Browse Prior Art Database

Chopper Wheel Gas Pulser for Foiless Anode E Beam Laser

IP.com Disclosure Number: IPCOM000089418D
Original Publication Date: 1977-Oct-01
Included in the Prior Art Database: 2005-Mar-05
Document File: 2 page(s) / 30K

Publishing Venue

IBM

Related People

Dreyfus, RW: AUTHOR [+2]

Abstract

Higher repetition rates are possible with the foiless anode E-beam laser by using a chopper wheel to reduce the volume of gas which must be pumped out after each shot while still having the gas reach the cathode with a large density gradient.

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Chopper Wheel Gas Pulser for Foiless Anode E Beam Laser

Higher repetition rates are possible with the foiless anode E-beam laser by using a chopper wheel to reduce the volume of gas which must be pumped out after each shot while still having the gas reach the cathode with a large density gradient.

After each shot of the foilless anode laser, the entire laser tube must ordinarily be evacuated in order to avoid shorting the field-emission diode through the gas from the previous shot. The time required for such evacuation is approximately 0.5 to 5 seconds depending upon the size of the pump.

In order to shorten this time so as to make repetition rates of 10 to 100 per second possible, a "chopper wheel" may be incorporated into the laser tube, as shown in the figure. Instead of introducing the laser gas from the right end 10 of electron drift tube 12 via a puff valve, the gas is now admitted through inlet 14, which may be positioned anywhere to the right of chopper wheel 16. The chopper wheel now acts as the gas valve. A port 18 in wheel 16 is brought into alignment with the tube by motor 20 for only a short period, e.g., 10/-4/ seconds. For a port diameter of 1 cm, this would require a wheel edge velocity of about 10/4/ cm/sec. In 10/-4/ seconds the gas will move about 2.5 cm into the diode region to the cathode 22. With a typical nitrogen density of about 4 x 10/17/ mol./cm for laser operation, this corresponds to only about 0.05 cm/3/ (STP) of gas, which may be ev...