E2V Technologies CX2668A, CX2668AX Air-Cooled, Hollow Anode, Two-Gap Metal/Ceramic Thyratrons

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E2V Technologies CX2668A, CX2668AX Air-Cooled, Hollow Anode, Two-Gap Metal/Ceramic Thyratrons The data to be read in conjunction with the Hydrogen Thyratron Preamble.

1 E2V Technologies CX2668A, CX2668AX Air-Cooled, Hollow Anode, Two-Gap Metal/Ceramic Thyratrons The data to be read in conjunction with the Hydrogen Thyratron Preamble. ABRIDGED DATA Hollow anode, deuterium-filled two-gap thyratrons with metal/ ceramic envelope, suitable for switching high peak and average power and long pulses, with 450% current reversal. The CX2668AX, which must be used in conjunction with E2V Technologies resistor box MA942A, permits a much larger variation in internal deuterium pressure than the CX2668A. Resistor box settings and/or reservoir heater voltage can be adjusted within the specified limits to obtain the maximum thyratron gas pressure consistent with the required voltage hold-off. Peak forward anode voltage kv max Peak forward anode current ka max Peak reverse anode current ka max Average anode current A max Operating frequency khz max GENERAL DATA Electrical Cathode.... barium aluminate impregnated tungsten Cathode heater voltage (see note 1) % V Cathode heater current A Reservoir heater voltage (see notes 1 and 2) % V Reservoir heater current A Tube heating time (minimum) min Mechanical Seated height mm ( inches) max Clearance required below mounting flange mm (2.953 inches) min Overall diameter (excluding connections) mm (4.803 inches) max Net weight kg (10.4 pounds) approx Mounting position seenote 3 Tube connections see outline Cooling The tube must be cooled by forced-air directed axially at the base from below. A fan of output 7.1 m 3 /min (250 ft 3 /min) minimum is necessary to maintain the tube temperatures within the limits specified. Air blown upwards at the base should be ducted via suitable apertures and cowlings to cool the grid flanges, tube envelope and anode, as indicated in Fig. 1. In addition to 300 W of heater power, the CX2668A/CX2668AX dissipate several hundred watts per ampere of average current. The cathode end of the tube must be cooled whenever heater voltages are applied. Envelope temperature: grid 1, grid 2, gradient grid and anode C max cathode flange and end cover C max PULSE MODULATOR SERVICE MAXIMUM AND MINIMUM RATINGS These ratings cannot necessarily be used simultaneously, and no individual rating must be exceeded. Min Max Anode Peak forward anode voltage (see note 4) kv Peak inverse anode voltage seenote 5 Peak forward anode current ka Peak reverse anode current seenote 5 Average anode current A Rate of rise of anode current.... see notes 6 and 7 E2V Technologies Limited, Waterhouse Lane, Chelmsford, Essex CM1 2QU England Telephone: +44 (0) Facsimile: +44 (0) enquiries@e2vtechnologies.com Internet: Holding Company: E2V Holdings Limited E2V Technologies Inc. 4 Westchester Plaza, PO Box 1482, Elmsford, NY USA Telephone: (914) Facsimile: (914) enquiries@e2vtechnologies.us # E2V Technologies Limited 2002 A1A-CX2668A, CX2668AX Issue 3, October /5672

2 6779 Cathode Heater voltage % V Heating time min Reservoir Heater voltage % V Heating time min NON-CONDUCTING SHROUD MOUNTING PLATE Fig. 1 Ducting of cooling air MAXIMUM AND MINIMUM RATINGS (Continued) Triggering For low rates of rise of anode current, the CX2668A and CX2668AX may be triggered with a pulse applied to grid 2 and a DC priming current applied to grid 1. For rates of rise of anode current in excess of 20 ka/ms, the CX2668A and CX2668AX must be triggered with two independent pulses. Min Max Grid 2 Unloaded grid 2 drive pulse voltage (see note 8) V Grid 2 pulse duration ms Rate of rise of grid 2 pulse (see note 9) kv/ms Grid 2 pulse delay (see note 10) ms Peak inverse grid 2 voltage V Loaded grid 2 bias voltage V Impedance of grid 2 drive circuit (see note 11) O Grid 1 Pulsed Unloaded grid 1 drive pulse voltage V Grid 1 pulse duration ms Rate of rise of grid 1 pulse kv/ms Peak inverse grid 1 voltage V Loaded grid 1 bias voltage see note 12 Peak grid 1 drive current (see note 13) A Grid 1 DC primed (See note 14) DC grid 1 unloaded priming voltage V DC grid 1 priming current A Environmental Ambient temperature C CHARACTERISTICS Min Typical Max Critical DC anode voltage for conduction kv Anode delay time ns Anode delay time drift (see note 15) ns Time jitter (see note 16) ns Recovery time see note 17 Cathode heater current (at 6.3 V) A Reservoir heater current (at 6.3 V) A NOTES 1. The cathode heater and the reservoir heater should be supplied from independent power supplies. The common connection for these two supplies is the yellow sleeved lead, not the cathode flange. N.B. The tube will suffer irreversible damage if the cathode flange is connected as the common point. The cathode heater supply must be connected between the cathode flange and the cathode heater lead (yellow sleeve), the reservoir heater supply must be connected between the cathode heater lead (yellow sleeve) and the reservoir heater lead (red sleeve), see Figs. 2 and 3. In order to meet the jitter specification, it may be necessary in some circumstances that the cathode heater be supplied from a DC source. 6625A END COVER CATHODE HEATER YELLOW Fig. 2 CX2668A base connections RESERVOIR HEATER RED DECOUPLING CAPACITORS MOUNTING FLANGE CX2668A, CX2668AX, page 2 # E2V Technologies

3 6350A END COVER CATHODE HEATER YELLOW Fig. 3 CX2668AX base connections RESERVOIR SYSTEM BLACK MOUNTING FLANGE RED DECOUPLING CAPACITORS Care should be taken to ensure that excessive voltages are not applied to the reservoir heater circuit from the cathode heater supply because of high impedance cathode heater connections. For example, in the worst case, an open circuit heater lead will impress almost double voltage on the reservoir heater, especially on switch-on, when the cathode heater impedance is minimal. This situation can be avoided by ensuring that the two supplies are in antiphase. The reservoir heater circuit must be decoupled with suitable capacitors, for example, a 1 mf capacitor in parallel with a low inductance 1000 pf capacitor. The heater supply systems should be connected directly between the cathode flange and the heater leads. This avoids the possibility of injecting voltages into the cathode and reservoir heaters. At high rates of rise of anode current, the cathode potential may rise significantly at the beginning of the pulse, depending on the cathode lead inductance, which must be minimised at all times. 2. CX2668AX gas pressure may be altered using E2V Technologies resistor box type MA942A. The CX2668AX must be used in conjunction with the MA942A. The resistor box must be connected between the reservoir monitor lead (black sleeve) and the cathode heater lead (yellow sleeve). Gas pressure may be increased by increasing the resistor box settings from their initial recommended values which accompany each delivered CX2668AX. The gas pressure may be increased to a value consistent with the required forward hold-off voltage. Additional variations in gas pressure can be achieved by altering the reservoir power supply voltage within the specified range. 3. The tube must be fitted using its mounting flange. 4. The maximum permissible peak forward voltage for instantaneous starting is 70 kv and there must be no overshoot. 5. Due to the bidirectional switching capability of the tube, the presence of any reverse voltages will result in reverse current. The higher the inverse current, the greater is the dissipation in the tube, and hence the average current at which the thyratron will operate satisfactorily is lower. 6. The ultimate value which can be attained depends to a large extent upon the external circuit. The rate of rise of current can be well in excess of 100 ka/ms. 7. This rate of rise refers to that part of the leading edge of the pulse between 10% and 90% of the pulse amplitude. 8. Measured with respect to cathode. 9. A lower rate of rise may be used, but this may result in the anode delay time, delay time drift and jitter exceeding the limits quoted. 10. The last 0.25 ms of the top of the grid 1 pulse must overlap the corresponding first 0.25 ms of the top of the delayed grid 2 pulse. 11. During both the drive pulse period and during recovery when the current flow is reversed. 12. DC negative bias voltages must not be applied to grid 1. When grid 1 is pulse driven, the potential of grid 1 may vary between 710 V and +5 V with respect to cathode potential during the period between the completion of recovery and the commencement of the succeeding grid pulse. 13. The optimum grid 1 pulse current is the maximum value which can be applied without causing premature commutation. This value is variable depending on gas pressure, maximum forward anode voltage, grid 2 negative bias voltage, peak current and repetition rate. 14. When DC priming is used on grid 1, a negative bias of 100 to 200 V must be applied to grid 2 to ensure anode voltage hold-off 15. Measured between the second minute after the application of HT and 30 minutes later. 16. A time jitter of less than 1 ns can be obtained if the cathode heater voltage is supplied from a DC source, by adopting double-pulsing, and by applying a grid 2 pulse with a rate of rise of voltage (unloaded) in excess of 20 kv/ ms. 17. The amount of time available for thyratron recovery must be maximised by circuit design, and reliable operation may necessitate the use of command charging techniques. The amount of time required for recovery is affected by gas pressure, peak current, pulse duration and load mismatch which keeps the thyratron in a conducting state. # E2V Technologies CX2668A, CX2668AX, page 3

4 OUTLINE OF CX2668AX (All dimensions without limits are nominal) CX2668A outline is identical, except that it has no monitor lead. POTENTIAL DIVIDER CONNECTION TAPPED 8-32 UNC 1C ANODE CONNECTION FITTED WITH 1 / 4-20 UNC SCREW 6778A GRID CONNECTIONS FITTED WITH 8-32 UNC SCREWS. SEE NOTE 1 1Q A 1R M GRID 2 GRID 1 L D N 1T P E MOUNTING FLANGE SEE NOTE 2 END COVER SEE NOTE 3 SEE NOTE 1 1F SEE NOTE 4 MONITOR LEAD (BLACK) G LONG, TAG TO SUIT 1S 1B RESERVOIR HEATER LEAD (RED) G LONG, TAG TO SUIT 1H CATHODE HEATER LEAD (YELLOW) G LONG, TAG TO SUIT 1H 6 HOLES 1J EQUISPACED ON K PCD. SEE NOTE 5 CX2668A, CX2668AX, page 4 # E2V Technologies

5 Ref Millimetres Inches A max max B C D E max max F max max G H J K L M N P Q R S T max max Inch dimensions have been derived from millimetres. Outline Notes 1. The holes for all grid connections are in line with the hole in the mounting flange to within +5 8 of the centre. 2. The mounting flange is the connection for the cathode and cathode heater return. 3. The end cover is at heater potential and must not be grounded. 4. The minimum recommended mounting hole is 78.0 mm (3.071 inches). 5. The holes in the mounting flange, the outside diameter of the stress rings and the outside diameter of the anode stud are concentric to within +1.0 mm (0.040 inch). HEALTH AND SAFETY HAZARDS E2V Technologies hydrogen thyratrons are safe to handle and operate, provided that the relevant precautions stated herein are observed. E2V Technologies does not accept responsibility for damage or injury resulting from the use of electronic devices it produces. Equipment manufacturers and users must ensure that adequate precautions are taken. Appropriate warning labels and notices must be provided on equipments incorporating E2V Technologies devices and in operating manuals. High Voltage Equipment must be designed so that personnel cannot come into contact with high voltage circuits. All high voltage circuits and terminals must be enclosed and fail-safe interlock switches must be fitted to disconnect the primary power supply and discharge all high voltage capacitors and other stored charges before allowing access. Interlock switches must not be bypassed to allow operation with access doors open. X-Ray Radiation All high voltage devices produce X-rays during operation and may require shielding. The X-ray radiation from hydrogen thyratrons is usually reduced to a safe level by enclosing the equipment or shielding the thyratron with at least 1.6 mm ( 1 / 16 inch) thick steel panels. Users and equipment manufacturers must check the radiation level under their maximum operating conditions. # E2V Technologies CX2668A, CX2668AX, page 5

6 SCHEMATIC DIAGRAM 6986 R 2 R 1 C 1 R 1 GRID 2 DELAYED WITH RESPECT TO GRID 1 GRID 2 VOLTAGE V, 1 ms R 2 C 1 R 1 G2 R 3 0 NEGATIVE BIAS VOLTAGE G1 CATHODE HEATER SUPPLY C 2 R 4 GRID 1 CURRENT 5 40A, 2 ms 1.0 ms TYPICAL GRID 1/GRID 2 DELAY C 3 RESERVOIR HEATER SUPPLY (VARIABLE) C 2 C 3 MA942A RECOMMENDED GRADIENT GRID, TRIGGER GRID, CATHODE AND RESERVOIR HEATER CONNECTIONS R 1 = 470 O 2.5 W vitreous enamelled wirewound resistors. R 2 = 5 to 20 MO high voltage resistors with a power rating consistent with forward anode voltage. R 3 = Grid 2 series resistor. 12 W vitreous enamelled wirewound is recommended, of an impedance to match the grid 2 drive pulse circuit. R 4 = Grid 1 series resistor. 12 W vitreous enamelled wirewound is recommended, of an impedance to match the grid 1 drive pulse circuit. C 1 = 300 to 500 pf capacitors with a voltage rating equal to the peak forward voltage. These capacitors may be necessary to divide the charging voltage properly when the charging time is less than 5 ms. C 2,C 3 = Reservoir protection capacitors with a voltage rating 5500 V; C 2 = 1000 pf low inductance (e.g. ceramic), C 3 = 1 mf (e.g. polycarbonate or polypropylene). Components R 3,R 4,C 2, and C 3 should be mounted as close to the tube as possible. Whilst E2V Technologies has taken care to ensure the accuracy of the information contained herein it accepts no responsibility for the consequences of any use thereof and also reserves the right to change the specification of goods without notice. E2V Technologies accepts no liability beyond that set out in its standard conditions of sale in respect of infringement of third party patents arising from the use of tubes or other devices in accordance with information contained herein. CX2668A, CX2668AX, page 6 Printed in England # E2V Technologies

CX1725W Liquid Cooled, Hollow Anode Two-Gap Metal/Ceramic Thyratron

CX1725W Liquid Cooled, Hollow Anode Two-Gap Metal/Ceramic Thyratron The data to be read in conjunction with the Hydrogen Thyratron Preamble. ABRIDGED DATA Hollow anode, deuterium-filled two-gap thyratrons