Dimensions and volume of a Cryogenic Zenon SEP propellant tank

All of these papers are for particle physics experiments. A cryogenic Xenon Tank embedded in a cryogenic chemical stage would have better mass fractions. Cryogenic Xenon would easily fit in a Hydrolox or Metholox in space stage

We propose a Hydrolox  SEP Gateway PPE stage!

it would also serve as a fuel depot and planetary probe, with a distributed launch and SEP you could get a fully fueled stage to an orbit injection burn at Pluto and the Ice Giants

IEPC1991-107

2011 IEPC High Power SEP for Expl paper19910002485

20030067928

From IEPC1991

     “Let us consider a few cases. We saw above that for tank pressure containment mass is inversely proportion ion engine operating on xenon at 5000  seconds I,p  signal to the propellant density. For the cryogenic case, at 30  kW, the tank heat load will need to be limited to one needs a somewhat larger safety factor because of 3  W. Liquid xenon has a density of 3.08 kg/I  at 165  K, possible temperature excursions, so using P = 3,  and so if we assume an initial 3000 kg  propellant load, the P =  1 atm = 101  kPa, we find that for a 3000 kg  initial tank will need a volume of 974 1. A  spherical tank of the propellant load in a titanium tank, xenon will require this volume will have a radius of .61  m and a surface only 1.5 kg for pressure containment, helium will area of 4.75 m2 “

Our Ice Giant Mission Tug would look like this https://yellowdragonblog.com/2017/12/16/ula-aces-espa-ring-outer-planet-probe-2-0/