What is thyratron in electronics

DATASHEETwww.perkinelmer.com/opto.DescriptionThyratrons are fast acting highvoltage switches suitable for avariety of applications includingradar, laser and scientific use. PerkinElmer’s thyratrons areconstructed of ceramic andmetal for strength and long life.Over 300 thyratron types areavailable from PerkinElmer. Thetypes listed in this guide are across section of the broad lineavailable. We encourageinquiries for thyratrons to suityour particular application.Features•Wide operating voltage range•High pulse rate capability•Ceramic-metal construction•High current capability•Long lifeThyratronsLightingImagingTelecomHigh Energy Switches
How a Thyratron worksThe operation of the device canbe divided into three phases: trig-gering and commutation (closure),steady-state conduction, andrecovery (opening), each of whichis discussed below.Triggering and CommutationWhen a suitable positive trigger-ing pulse of energy is applied tothe grid, a plasma forms in thegrid-cathode region from elec-trons. This plasma passes throughthe apertures of the grid structureand causes electrical breakdownin the high-voltage regionbetween the grid and the anode. This begins the process of thyra-tron switching (also called com-mutation). The plasma that isformed between the grid and theanode diffuses back through thegrid into the grid-cathode space."Connection" of the plasma in theanode-grid space with the plasmain the cathode-grid space com-pletes the commutation process.The commutation process is sim-ply modeled as shown in Figure 2. The time interval between triggerbreakdown of the grid-cathoderegion and complete closure ofthe thyratron is called the anodedelay time. It is typically 100-200nanoseconds for most tube types.During commutation, a high volt-age spike appears at the grid ofthe thyratron. This spike happensin the time it takes for the plasmain the grid-anode space to "con-nect" to the plasma in the grid-cathode space. During this time,the anode is momentarily "con-nected" to the grid thereby caus-ing the grid to assume a voltagenearly that of the anode’s.Although the grid spike voltage isbrief in duration, usually less than100 nS, it can damage the griddriver circuit unless measures are taken to suppress the spikebefore it enters the grid driver cir-cuit. The location of the grid spikesuppression circuit is shown inFigure 3, Grid Circuit.Figure 4, Typical Grid SpikeSuppression Circuits, shows themore common methods used toprotect the grid driver circuit. Inusing any of these types of cir-cuits, care must be exercised toassure that the Grid Driver Circuitpulse is not attenuated in an unac-ceptable manner. The values forthe circuit components aredependent on the characteristicsof the thyratron being driven, theANODECONTROL GRID (G2)AUXILIARY GRID (G1)CATHODEFigure 1. Thyratron with auxiliary grid (heater detail not shown)ee1. Trigger pulse applied to control grid.2. Grid-cathode breakdown.3. Electrons from grid-cathode region create a dense plasma in the grid-anode region. The plasma front propagates to- ward the cathode via break- down of gas.4. ClosureFigure 2. Thyratron commutationPropagatingPlasma Front