Hi Entechbob,
Thank you for reply. OK. Sounds solid. That explains your need for boost converter. The chip you are planning to use, the LT1111 looks like a perfect fit. You only need to be careful not to short the output, as there is no short circuit protection, but that is perhaps not so critical in this case.
As your application is battery operated, you could also extend the battery life by fiddling the power consumption of the pulse source. The epic 555 chip consumes around 10mA all the time. That may become the major consumer, if your solenoid firing interval is long. You could consider a low power drop-in version of the timer, such as TLC555, reducing the Iq to 250uA.
https://www.digikey.com/en/products/detail/texas-instruments/TLC555CDR/276979
Cheers,
heke
AsamaLab