Geant4 Simulations for the Radon Electric Dipole Moment Search at

a measurement cell. The RnEDM experiment will implant a beam of Rn ions (likely
221 Rn or 223 Rn) into a thin foil located in the target chamber. The collected Rn
atoms are then transferred into the measurement cell via the transfer chamber using
techniques discussed in the following section.
2.2.1 Transferring Radioactive Noble Gas Isotopes
Theprocessoftransferringradioactivenoblegasisotopeson-linetoameasurement
cellhasbeenshowntobesuccessful atTRIUMF[26]. Aprototypenoblegascollection
apparatus, shown inFigure2.2, wastestedwith 120 Xeasbeamsofradonisotopeswere
not available at the time of the tests. The 120 Xe isotope was chosen due its half-life of
40 minutes, comparable to the roughly 25 minute half-lives of 221 Rn and 223 Rn. An
initial beam of 120 Cs produced the 120 Xe isotopes through β decay; the decay chain
is shown in Equation 2.2. The beam was implanted in a thin zirconium foil for about
two 120 Xe half-lives, after which the remaining 120 Cs atoms were given roughly 10
minutes to decay into 120 Xe.
120 Cs(64 s) → 120 Xe(40 m) → 120 I(81 m) → 120 Te(stable) . (2.2)
Valve V1 was closed to separate the target chamber from the beam line. Heating the
zirconium foil to about 1350 K released the xenon atoms into the target chamber volume.
OpeningtheV2valveallowedthexenongastodiffuseintothetransferchamber,
where the xenon atoms froze onto a pre-cooled coldfinger. After cryopumping, the
V2 valve was closed and V3 to the cell was opened while simultaneously warming the
coldfinger to release the xenon gas. Once the coldfinger was warmed, the V4 valve
was opened which released a ballest volume of N 2 gas into the transfer chamber. The
N 2 gas expanded and pushed the xenon gas into the measurement cell. The V3 valve
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