extend electron range tables up to 1 TeV

1 files changed, 235 insertions, 0 deletions

diff --git a/src/extend-electron-range-table.c b/src/extend-electron-range-table.c
new file mode 100644
index 0000000..89901df
--- /dev/null
+++ b/src/extend-electron-range-table.c
@@ -0,0 +1,235 @@
+/* Copyright (c) 2019, Anthony Latorre <tlatorre at uchicago>
+ *
+ * This program is free software: you can redistribute it and/or modify it
+ * under the terms of the GNU General Public License as published by the Free
+ * Software Foundation, either version 3 of the License, or (at your option)
+ * any later version.
+
+ * This program is distributed in the hope that it will be useful, but WITHOUT
+ * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
+ * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for
+ * more details.
+
+ * You should have received a copy of the GNU General Public License along with
+ * this program. If not, see <https://www.gnu.org/licenses/>.
+ */
+
+#include <stdio.h>
+#include <gsl/gsl_spline.h>
+#include <stdlib.h> /* for size_t, strtod() */
+#include <errno.h> /* for errno */
+#include <string.h> /* for strerror(), strtok() */
+#include "sno.h"
+#include "misc.h"
+
+static double *x, *dEdx_rad, *dEdx;
+static size_t size;
+
+static gsl_interp_accel *acc_dEdx_rad;
+static gsl_spline *spline_dEdx_rad;
+
+static gsl_interp_accel *acc_dEdx;
+static gsl_spline *spline_dEdx;
+
+static int init()
+{
+    int i, j;
+    char line[256];
+    char *str;
+    double value;
+    int n;
+
+    FILE *f = fopen("e_water_liquid.txt", "r");
+
+    if (!f) {
+        fprintf(stderr, "failed to open e_water_liquid.txt: %s\n", strerror(errno));
+        return -1;
+    }
+
+    i = 0;
+    n = 0;
+    /* For the first pass, we just count how many values there are. */
+    while (fgets(line, sizeof(line), f)) {
+        size_t len = strlen(line);
+        if (len && (line[len-1] != '\n')) {
+            fprintf(stderr, "got incomplete line on line %i: '%s'\n", i, line);
+            goto err;
+        }
+
+        i += 1;
+
+        /* Skip the first 8 lines since it's just a header. */
+        if (i <= 8) continue;
+
+        if (!len) continue;
+        else if (line[0] == '#') continue;
+
+        str = strtok(line," \n");
+
+        while (str) {
+            value = strtod(str, NULL);
+            str = strtok(NULL," \n");
+        }
+
+        n += 1;
+    }
+
+    x = malloc(sizeof(double)*n);
+    dEdx_rad = malloc(sizeof(double)*n);
+    dEdx = malloc(sizeof(double)*n);
+    size = n;
+
+    i = 0;
+    n = 0;
+    /* Now, we actually store the values. */
+    rewind(f);
+    while (fgets(line, sizeof(line), f)) {
+        size_t len = strlen(line);
+        if (len && (line[len-1] != '\n')) {
+            fprintf(stderr, "got incomplete line on line %i: '%s'\n", i, line);
+            goto err;
+        }
+
+        i += 1;
+
+        /* Skip the first 8 lines since it's just a header. */
+        if (i <= 8) continue;
+
+        if (!len) continue;
+        else if (line[0] == '#') continue;
+
+        str = strtok(line," \n");
+
+        j = 0;
+        while (str) {
+            value = strtod(str, NULL);
+            switch (j) {
+            case 0:
+                x[n] = value;
+                break;
+            case 2:
+                dEdx_rad[n] = value;
+                break;
+            case 3:
+                dEdx[n] = value;
+                break;
+            }
+            j += 1;
+            str = strtok(NULL," \n");
+        }
+
+        n += 1;
+    }
+
+    fclose(f);
+
+    acc_dEdx_rad = gsl_interp_accel_alloc();
+    spline_dEdx_rad = gsl_spline_alloc(gsl_interp_linear, size);
+    gsl_spline_init(spline_dEdx_rad, x, dEdx_rad, size);
+
+    acc_dEdx = gsl_interp_accel_alloc();
+    spline_dEdx = gsl_spline_alloc(gsl_interp_linear, size);
+    gsl_spline_init(spline_dEdx, x, dEdx, size);
+
+    return 0;
+
+err:
+    fclose(f);
+
+    return -1;
+}
+
+/* Returns the approximate dE/dx for a electron in water with kinetic energy
+ * `T`. If `T` is outside the bounds of the range table, extrapolate linearly
+ * using the last two points.
+ *
+ * `T` should be in MeV and `rho` in g/cm^3.
+ *
+ * Return value is in MeV/cm.
+ *
+ * See http://pdg.lbl.gov/2018/AtomicNuclearProperties/adndt.pdf. */
+double electron_get_dEdx(double T, double rho)
+{
+    if (T < spline_dEdx->x[0]) {
+        return spline_dEdx->y[0];
+    } else if (T < spline_dEdx->x[size-1]) {
+        return gsl_spline_eval(spline_dEdx, T, acc_dEdx)*rho;
+    }
+
+    /* We extrapolate using the last two points. */
+    return spline_dEdx->y[size-1] + (spline_dEdx->y[size-1]-spline_dEdx->y[size-2])*(T-spline_dEdx->x[size-1])/(spline_dEdx->x[size-1]-spline_dEdx->x[size-2]);
+}
+
+/* Returns the approximate radiative dE/dx for a electron in water with kinetic
+ * energy `T`. If `T` is outside the bounds of the range table, extrapolate
+ * linearly using the last two points.
+ *
+ * `T` should be in MeV and `rho` in g/cm^3.
+ *
+ * Return value is in MeV/cm.
+ *
+ * See http://pdg.lbl.gov/2018/AtomicNuclearProperties/adndt.pdf. */
+double electron_get_dEdx_rad(double T, double rho)
+{
+    if (T < spline_dEdx_rad->x[0]) {
+        return spline_dEdx_rad->y[0];
+    } else if (T < spline_dEdx_rad->x[size-1]) {
+        return gsl_spline_eval(spline_dEdx_rad, T, acc_dEdx_rad)*rho;
+    }
+
+    /* We extrapolate using the last two points. */
+    return spline_dEdx_rad->y[size-1] + (spline_dEdx_rad->y[size-1]-spline_dEdx_rad->y[size-2])*(T-spline_dEdx_rad->x[size-1])/(spline_dEdx_rad->x[size-1]-spline_dEdx_rad->x[size-2]);
+}
+
+double electron_get_range(double T0)
+{
+    double T, dx, range;
+
+    T = T0;
+
+    dx = 1e-5;
+
+    range = 0.0;
+    while (T > 0) {
+        double dEdx2 = electron_get_dEdx(T, WATER_DENSITY);
+        T -= dEdx2*dx;
+        range += dx;
+    }
+
+    return range;
+}
+
+int main(int argc, char **argv)
+{
+    int i;
+    double T0;
+    double Ts[18] = {
+        2.000E+04,
+        3.000E+04,
+        4.000E+04,
+        5.000E+04,
+        6.000E+04,
+        7.000E+04,
+        8.000E+04,
+        9.000E+04,
+        1.000E+05,
+        2.000E+05,
+        3.000E+05,
+        4.000E+05,
+        5.000E+05,
+        6.000E+05,
+        7.000E+05,
+        8.000E+05,
+        9.000E+05,
+        1.000E+06};
+
+    init();
+
+    for (i = 0; i < LEN(Ts); i++) {
+        T0 = Ts[i];
+
+        printf("%.3E - %.3E %.3E %.3E - -\n", T0, electron_get_dEdx_rad(T0,WATER_DENSITY), electron_get_dEdx(T0,WATER_DENSITY), electron_get_range(T0));
+    }
+
+    return 0;
+}