Will this ion reach the sensitive volume, and at what LET?
Pick a facility beam or define your own, stack every window, air gap, degrader and package layer in front of the part, and read the LET, the range left and where the ion sits on its Bragg curve when it gets to the silicon.
Beam
Tilt and target
Sensitive volume
Layer stack, beam to device
| # | Material | Thick | Unit | Rotθ |
|---|
At the device
Through the stack
| Layer | Eff. thick mm | Entry E MeV/u | Exit E MeV/u | Entry LET | Exit LET | Range left in layer, mm |
|---|
Every ion in this cocktail, through your stack
Same stack, tilt and target for each beam in the selected cocktail. The bar is how deep the ion gets below the surface and the white tick is the bottom of the sensitive volume. Click a row to use that beam.
Which facility can reach it?
Define the device overlayers above the sensitive volume, an effective-LET window, a minimum range left in the sensitive volume and a minimum air gap. The finder sweeps every facility and cocktail ion across tilt, degrader and air gap, and lists what can meet the spec. Overlayers rotate with the part. Configurations degraded past the Bragg peak (the ion arrives below the peak energy: ambiguous LET, short range, severe straggling) are rejected by default.
| # | Material | Thick | Unit |
|---|
| Facility | Ion | E, MeV/u | Angle | Degrader | Air, mm | Eff LET | Surf LET | Range, µm | E at SV MeV/u | Peak side | Achievable eff-LET span |
|---|
How it works
Three steps from the beam line to the junction
Start from the beam energy
Each cocktail ion leaves the accelerator with a quoted energy per nucleon. Pick a facility beam, or any of the 74 ions and an energy for a custom beam.
Lose energy on the way in
The window, air, degraders and package layers each take energy out, and layers that tilt with the part are crossed at t/cosθ. The solver sizes a degrader for the LET you ask for.
Read LET and range at depth
The range left sets the energy at each depth below the surface, and the energy sets the LET the sensitive volume sees, up to the Bragg peak and the end of the track.
How the numbers are computed
The calculator follows the ion layer by layer with the range-energy method. For each material and ion it holds SRIM-derived tables of LET and range against energy per nucleon. Entering a layer at energy Ein, the ion has range R(Ein) in that material; crossing an effective thickness t leaves R(Ein) − t, and the same table read the other way gives the exit energy. Tables are interpolated log-log and extrapolated the same way past their ends.
A layer marked to rotate is crossed at t/cosθ. Thicknesses in mil, µm, mm or mg/cm² are converted to mm, the last through the material density. LET is the mass stopping power in MeV·cm²/mg.
At the device, the surface LET is the target material's LET at the exit energy and the range left is its range at that energy, both along the track. The effective LET is the surface LET divided by cosθ, the cosine law for a thin sensitive volume.
A depth z below the surface is reached after a track length z/cosθ. The range left there sets the energy and the energy sets the LET, which gives the LET-against-depth curve. The energy left in the sensitive volume is that LET integrated along the track between its top and bottom, times the density. In silicon, at 3.6 eV per electron-hole pair, 1 MeV·cm²/mg over 1 µm of track is about 0.0104 pC.
The Bragg-peak check compares the energy at the device with the energy of the LET maximum in the target material: below it is the back of the peak, up to 30 percent above it is the steep shoulder, and above that is the front.
The degrader solver adds a layer of the facility's first degrader material (aluminum when the facility has none) and finds by bisection the thickness that gives the requested surface LET, searching only up to the thickness that reaches the Bragg peak. When the facility's degraders include aluminum it also lists single-foil and tilt combinations with the same effective thickness.
The facility finder tries every facility and cocktail ion against air gaps from your minimum up to 100 mm (none for facilities without an air gap), the facility's degrader options (every subset sum for foil ladders that stack, 1 to 10 mil for aluminum-only sets, combinations otherwise) and tilts from 0 to the facility's limit in 3 degree steps, with your overlayers rotating with the part. With both LET bounds it keeps the simplest recipe inside the window; with one bound it treats it as a target to reach and keeps the recipe with the most range to spare. Recipes that leave the ion past the Bragg peak are hidden unless you ask for them.
Assumptions and limits
The track is straight and every ion has the mean range: no range or energy straggling, no multiple scattering, no nuclear reactions or fragments. Straggling matters most near the end of range and past the Bragg peak, which is why those cases are flagged.
The cosine law behind the effective LET holds for thin, wide sensitive volumes. It does not hold for deep volumes such as latchup wells or power devices, where the LET along the track and the depth reached are what count.
Facility energies are taken as each facility quotes them: in vacuum for some, after the exit window for others (see the facility note). The default window and air layers follow from that; check them against the facility's own setup.
Aramica, Mylar and PEN windows use Kapton mass stopping at their own densities, which is provisional until facility-specific data are added. Co-59 is interpolated between Fe-56 and Ni-58.
Use the results for test planning, and check critical values against the facility's dosimetry.
Check the numbers facility values against this calculator
Published LET values for the selected cocktail against this calculator, with the facility's standard setup. The engine matches the MSU KSEE cocktail and SEUSS LET output to about 1 percent, the NSRL SEE library to about 0.5 percent in LET and 2 percent in range, and the NSRL SRIM StackUp spreadsheet to about 0.1 percent per layer.
Data and provenance materials, facilities, sources
Every material below can be used for any layer, for the target and for the finder's overlayers. Composition fractions are as recorded with the stopping tables, some by atom and some by mass.
Save and load files
Save layers downloads a JSON file with the facility, ion, energy, tilt, target, the layer stack (material, thickness, unit and whether it rotates), the sensitive volume depths and the finder's overlayers. Load layers reads it back; files saved by the earlier version of this page, without the sensitive volume and overlayers, still load. Nothing is stored in the browser.
References
J. F. Ziegler, M. D. Ziegler and J. P. Biersack, "SRIM, the stopping and range of ions in matter (2010)," Nucl. Instrum. Methods Phys. Res. B, vol. 268, pp. 1818-1823, 2010.
NASA Space Radiation Laboratory, Brookhaven National Laboratory, SRIM StackUp spreadsheet, version 12: the source of the stopping and range tables.
Facility beam lists: Texas A&M University Cyclotron Institute (K500 and K150), LBNL 88-Inch Cyclotron BASE, Michigan State University FRIB (KSEE and FSEE) and the NSRL SEE library.