Switch Modules can be stacked to achieve desired voltage.
Press Release Summary:

Original Press Release:
Solid-State Switch Modules Stackable To Achieve Desired Voltage
An expanded line of solid-state switch modules that are field-proven for use as transmitter modulators in radar systems and as critical components in high-energy physics and semiconductor fabrication systems is being introduced by Diversified Technologies, Inc. of Bedford, Massachusetts.
DTI PowerMod(TM) Solid-State Switch Modules feature >99% switching efficiency or <60 V drop for a 9 kV, 30 A module and are immune to arcing, emissions, and the other lifetime limiting factors associated with conventional vacuum tubes. Easy to install and maintain, these compact modules are available
as 6 kV (500 kW peak power), 9 kV (270 kW peak), and 12 kV (1 MW peak) plates which can be stacked to achieve the desired voltage.
Fully qualified for military shipboard applications, DTI PowerMod(TM) Solid-State Switch Modules provide one million hours predicted reliability per MIL-HDBK-217F, these solid-state switch modules require only a dc voltage source and input signal, and can be passively air cooled. Individual modules measure only 7" x 7" x 3" (6 and 9 kV) and 12" x 12" x 3" (12 kV).
DTI PowerMod(TM) Solid-State Switch Modules are priced from $2,500. each, depending upon configuration and quantity.