What you have there is basically a fluorescent lamp sans phosphor and protective uv glass. These generally need high voltage to start so I would see if you can find a 5 watt pl fluorescent ballast (usually a couple bucks on eBay.) When this bulb starts the filament warms up, vaporizing the mercury and then an arc strikes between the top points of the filament. A six watt fluorescent tube takes about 55 volts to strike so i would estimate yours to possibly need a striking voltage of at least 35-40 volts DC.