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Schematic of the apparatus. Protons with $\SI{1.4}{\giga\electronvolt}$ produce radioisotopes through nuclear reactions in the target material, where tin isotopes are vaporized and then laser-ionized through resonance laser ionization (laser scheme in insert a). Here, IP stands for the ionization potential of tin, and AI denotes the energy for auto-ionizing states. Tin isotopes (red circles) and parasitically ionized contamination (blue and white circles) are extracted at $\SI{30}{\kilo\electronvolt}$ and subsequently mass separated using two electromagnets (High-Resolution Separator, HRS). Ions with the selected mass-over-charge ratio $m/q$ are collected in an ion cooler and buncher (RFQ-cb). The beam is then released in bunches, reduced in energy through the pulsed-drift tube to $\SI{3.2}{\kilo\electronvolt}$, and captured in a time-of-flight spectrometer (MR-ToF MS) at $\SI{2}{\kilo\electronvolt}$. After about $\SI{50}{\milli\second}$, the ions are released, and their flight time to an ion detector is measured. An example ToF spectrum for $m/q=106$ showing strontium-fluoride, indium, and tin is depicted in insert b).

Left: Normalized yields (in ions per second normalized to $\SI{1}{\micro\ampere}$ of protons on target) of the extracted $^{106}$Sn$^+$ beam as measured by ISOLTRAP throughout the experiment with respect to target and ion source temperatures. The temperatures were calibrated using an optical pyrometer for a range of applied heating currents and powers, with measurement uncertainties of about $\SI{50}{\celsius}$ (not shown). Shaded areas indicate where protons from the PSB were not available. The grey dashed line indicates the temperature at which the target material starts to undergo sintering. Right: Normalized yield and beam purity (percentage of tin ions in the MR-ToF spectrum) of the extracted $^{106}$Sn$^+$ beam versus ion-source temperature. The target temperature in the shaded area was $\SI{1650\pm 50}{\celsius}$, in the nonshaded area $\SI{1730\pm 50}{\celsius}$.

Best yields extracted from the target measured with the MR-ToF MS (red) and normalized to a proton current of $\SI{1}{\micro\ampere}$. In comparison, previously measured yields of extracted beams reported in the ISOLDE yield database (blue) and in-target production simulation codes FLUKA~\cite{2014_Bohlen_FLUKA, Ahdida_2022_FLUKA} and ABRABLA~\cite{2009_Kelic_ABRABLA}, as well as the empirical fragmentation production cross section code EPAX-V3~\cite{2012_Summerer_EPAX_V3}.

Typical ToF spectra for the four tin isotopes investigated in the present study. The grey-shaded area indicates the fit range, which excludes the potentially saturated peaks at smaller ToFs. The red line shows the fit to the data. The horizontal axis is centered at the indium peak.

Evaluated two-neutron separation energy (top) and odd-even staggering estimator (bottom) from masses reported in the \texttt{AME2020} (grey), the ISOLTRAP measurement with adjustments (red), nuclear \textit{ab initio} calculations from~\cite{2021_Mougeot}, and DFT calculations from~\cite{Erler2012}. The grey data points include the masses of $^{101-103}$Sn calculated with the $Q_{\textrm{EC}}$ value measurements from~\cite{Straub2010, Faestermann2002, Kavatsyuk2005}. The red points include this work's mass measurement of $^{103}$Sn and the extrapolated mass value for $^{101}$Sn.

Evaluated two-neutron separation energy from masses reported in the \texttt{AME2020} including the masses of $^{101-103}$Sn calculated from $Q_{\textrm{EC}}$ value measurements~\cite{Straub2010, Faestermann2002, Kavatsyuk2005} (grey) or readjusted as shown in Tab.~\ref{tab:AMEupdate} following the ISOLTRAP mass measurements from this work (red). Plotted improvements on indium mass uncertainties are taken from~\cite{2021_Mougeot, 2023_Nies_In}.