LS-5101

DATASHEET Lighting Imaging Telecom High Energy Switches Thyratrons Description Thyratrons are fast acting high voltage switches suitable for a variety of applications including radar, laser and scientific use. PerkinElmer’s thyratrons are constructed of ceramic and metal for strength and long life. Over 300 thyratron types are available from PerkinElmer. The types listed in this guide are a cross section of the broad line available. We encourage inquiries for thyratrons to suit your particular application. Features • Wide operating voltage range • High pulse rate capability • Ceramic-metal construction • High current capability • Long life . www.perkinelmer.com/opto How a Thyratron works The operation of the device can be divided into three phases: triggering and commutation (closure), steady-state conduction, and recovery (opening), each of which is discussed below. The commutation process is simply modeled as shown in Figure 2. The time interval between trigger breakdown of the grid-cathode region and complete closure of the thyratron is called the anode delay time. It is typically 100-200 nanoseconds for most tube types. During commutation, a high voltage spike appears at the grid of the thyratron. This spike happens in the time it takes for the plasma in the grid-anode space to "connect" to the plasma in the gridcathode space. During this time, the anode is momentarily "connected" to the grid thereby causing the grid to assume a voltage nearly that of the anode’s. Although the grid spike voltage is brief in duration, usually less than 100 nS, it can damage the grid driver circuit unless measures are taken to suppress the spike before it enters the grid driver circuit. The location of the grid spike suppression circuit is shown in Figure 3, Grid Circuit. Figure 4, Typical Grid Spike Suppression Circuits, shows the more common methods used to protect the grid driver circuit. In using any of these types of circuits, care must be exercised to assure that the Grid Driver Circuit pulse is not attenuated in an unacceptable manner. The values for the circuit components are dependent on the characteristics of the thyratron being driven, the ANODE CONTROL GRID (G2) AUXILIARY GRID (G1) CATHODE Figure 1. Thyratron with auxiliary grid (heater detail not shown) Triggering and Commutation When a suitable positive triggering pulse of energy is applied to the grid, a plasma forms in the grid-cathode region from electrons. This plasma passes through the apertures of the grid structure and causes electrical breakdown in the high-voltage region between the grid and the anode. This begins the process of thyratron switching (also called commutation). The plasma that is formed between the grid and the anode diffuses back through the grid into the grid-cathode space. "Connection" of the plasma in the anode-grid space with the plasma in the cathode-grid space completes the commutation process. e e 1. Trigger pulse applied to control grid. 2. Grid-cathode breakdown. Propagating Plasma Front 3. Electrons from grid-cathode region create a dense plasma in the grid-anode region. The plasma front propagates toward the cathode via breakdown of gas. 4. Closure Figure 2. Thyratron commutation grid driver circuit design, and the performance required from the thyratron itself. Contact the applications engineering department at PerkinElmer to discuss the specific details of your requirement. Conduction Once the commutation interval has ended, a typical hydrogen thyratron will conduct with nearly constant voltage drop on the order of 100 volts regardless of the current through the tube. Recovery Thyratrons open (recover) via diffusion of ions to the tube inner walls and electrode surfaces, where the ions can recombine with electrons. This process takes from 30 to 150 microseconds, depending on the tube type, fill pressure, and gas (hydrogen or deuterium). The theoretical maximum pulse repetition rate is the inverse of the recovery time. Recovery can be promoted by arranging to have a small negative DC bias voltage on the control grid when forward conduction has ceased. A bias voltage of 50 to 100 volts is usually sufficient. Recovery can also be improved by arranging to have small negative voltage on the anode after forward conduction has ceased. In many radar circuits, a few-percent negative mismatch between a pulse-forming network and the load ensures a residual negative anode voltage. In laser circuits, classical pulse-forming networks are seldom used, so inverse anode voltage may not be easily generated. Recovery then strongly depends on the characteristics of the anode charging circuit. In general, charging schemes involving gently rising voltages (i.e., resonant charging and ramp charging) favor thyratron recovery, and therefore allow higher pulse repetition rates. Fast ramping and resistive charging put large voltages on the anode quickly, thus making recovery more difficult. The ideal charging scheme from the viewpoint of thyratron recovery is command charging, wherein voltage is applied to the thyratron only an instant before firing. CURRENT LIMITING AND/OR MATCHING RESISTOR GRID SPIKE SUPPRESSION CIRCUIT GRID DRIVER CIRCUIT Figure 3. Grid Circuit (a) Filter (b) Zener (c) MOV (d) Spark Gap Figure 4. Typical Grid Spike Suppression Circuits Thyratrons Plate Dissipation Factor Pb (x 109) 2.7 5 5 5 10 10 10 10 50 50 40 50 50 50 50 50 50 50 160 100 50 50 100 50 50 50 100 100 100 200 Peak Forward Grid Voltage egy (Min) 175 150 150 150 200 200 175 20 1500 450 450 500 500 500 500 500 500 500 1300 1300 500 500 500 500 450 500 2500 2500 2500 2500 Type HY-2 HY-6 HY-60 HY-61 HY-10 HY-11 HY-1A HY-1102 HY-3192 HY-32 HY-3204 1802 HY-3002 HY-3003 HY-3004 HY-3005 HY-3025 HY-3189 HY-5 HY-53 LS-3101S LS-4101 LS-4111 HY-3246 LS-3229 HY-3202 LS-5001 LS-5002 LS-5101 LS-5111 Peak Anode Voltage epy (kV) 8 16 16 16 20 18 18 18 32 32 32 25 25 35 25 35 28 32 40 40 35 40 40 45 70 32 40 50 40 40 Peak Anode Current ib (a) 100 350 350 350 500 1600 500 1000 1000 1500 1500 5000 5000 5000 5000 5000 5000 5000 5000 5000 5000 12000 12000 15000 15000 20000 20000 20000 20000 20000 Average Anode Current lb (Adc) 0.1 0.5 0.5 0.5 0.5 0.5 0.5 0.5 2.2 2.2 1 2.2 2.2 2.2 2.2 2.2 2.2 2.2 8 4 2 3 3 2 2 0.5 4 4 4 4 RMS Anode Current lp (Aac) 2 6.5 6.5 6.5 8 8 8 16 47.5 47.5 25 47.5 47.5 47.5 47.5 47.5 47.5 47.5 125 90 45 55 55 45 45 47.5 90 70 90 90 Cathode Heater V/A 6.3/3.5 6.3/7 6.3/7 6.3/8.5 6.3/7.5 6.3/7.5 6.3/11 6.3/7.5 6.3/12.5 6.3/18 6.3/18 6.3/12.5 6.3/12.5 6.3/12.5 6.3/12.5 6.3/12.5 6.3/12.5 6.3/12.5 6.3/30 6.3/30 6.3/18 6.3/28 6.3/28 6.3/16 6.3/16 6.3/18 6.3/29 6.3/35 6.3/29 6.3/29 Reservoir Heater V/A Note 1 6.3/2.5 6.3/7 Note 1 6.3/4 6.3/4 Note 1 6.3/8 6.3/5.5 6.3/5.5 6.3/6 6.3/5.5 6.3/5.5 6.3/5.5 6.3/5.5 6.3/5.5 6.3/5.5 6.3/5.5 4.5/11 4.5/11 6.3/6 6.3/6 6.3/6 6.3/6 6.3/6 6.3/13 4.5/10 4.5/15 4.5/10 4.5/10 Impedence of Grid Circuits g (Max) 1200 1500 1500 1500 500 500 500 500 250 400 400 400 400 400 400 400 250 250 100 100 250 250 250 250 400 250 50 100 50 50 EIA Type & Comments JAN 7621 JAN 7782 JAN 7665A Notes 1 Seated Height x Tube Width (Inches) 2.35 x 1.0 2 x 1.4 2.4 x 1.4 1 JAN 7620 3.6 x 1.4 3.4 x 2 2.2 x 2.25 JAN8613 1 2 3 4 5x2 2x2 3.75 x 3.25 4 x 3.25 3x6 4 x 3.25 4 x 3.25 4 x 3.25 4.75 x 3.25 ib to 10kA @