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#include <stdio.h>
#include <errno.h>
#include <string.h>
#include <stdlib.h>
#include <gsl/gsl_errno.h>
#include <gsl/gsl_spline.h>
#include <math.h>
static int initialized = 0;
static double *x, *dEdx, *csda_range;
static size_t size;
static gsl_interp_accel *acc_dEdx;
static gsl_spline *spline_dEdx;
static gsl_interp_accel *acc_range;
static gsl_spline *spline_range;
static const double MUON_CRITICAL_ENERGY = 1.029e6;
static int init()
{
int i, j;
char line[256];
char *str;
double value;
int n;
FILE *f = fopen("muE_water_liquid.txt", "r");
if (!f) {
fprintf(stderr, "failed to open muE_water_liquid.txt: %s", 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 10 lines since it's just a header. */
if (i <= 10) continue;
if (!len) continue;
else if (line[0] == '#') continue;
else if (strstr(line, "Minimum ionization")) continue;
else if (strstr(line, "Muon critical energy")) continue;
str = strtok(line," \n");
while (str) {
value = strtod(str, NULL);
str = strtok(NULL," \n");
}
n += 1;
}
x = malloc(sizeof(double)*n);
dEdx = malloc(sizeof(double)*n);
csda_range = 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 10 lines since it's just a header. */
if (i <= 10) continue;
if (!len) continue;
else if (line[0] == '#') continue;
else if (strstr(line, "Minimum ionization")) continue;
else if (strstr(line, "Muon critical energy")) continue;
str = strtok(line," \n");
j = 0;
while (str) {
value = strtod(str, NULL);
/* According to the file, the values are stored for wavelengths
* between 230 and 700 in 1 nm increments. */
switch (j) {
case 0:
x[n] = value;
break;
case 7:
dEdx[n] = value;
break;
case 8:
csda_range[n] = value;
break;
}
j += 1;
str = strtok(NULL," \n");
}
n += 1;
}
fclose(f);
acc_dEdx = gsl_interp_accel_alloc();
spline_dEdx = gsl_spline_alloc(gsl_interp_linear, size);
gsl_spline_init(spline_dEdx, x, dEdx, size);
acc_range = gsl_interp_accel_alloc();
spline_range = gsl_spline_alloc(gsl_interp_linear, size);
gsl_spline_init(spline_range, x, csda_range, size);
initialized = 1;
return 0;
err:
fclose(f);
return -1;
}
double get_range(double T, double rho)
{
/* Returns the approximate range a muon with kinetic energy `T` will travel
* in water before losing all of its energy. This range is interpolated
* based on data from the PDG which uses the continuous slowing down
* approximation.
*
* `T` should be in MeV, and `rho` should be in g/cm^3.
*
* Return value is in cm.
*
* See http://pdg.lbl.gov/2018/AtomicNuclearProperties/adndt.pdf. */
if (!initialized) {
if (init()) {
exit(1);
}
}
return gsl_spline_eval(spline_range, T, acc_range)/rho;
}
double get_E(double T, double x, double rho)
{
/* Returns the approximate energy of a muon in water after travelling `x`
* cm with an initial kinetic energy `T`.
*
* `T` should be in MeV, `x` in cm, and `rho` in g/cm^3.
*
* Return value is in MeV.
*
* See http://pdg.lbl.gov/2018/AtomicNuclearProperties/adndt.pdf. */
double a, b, range, E;
if (!initialized) {
if (init()) {
exit(1);
}
}
range = gsl_spline_eval(spline_range, T, acc_range)/rho;
/* FIXME: Need to double check if it's kosher to be using kinetic energies
* here instead of the total energy. Equation 1 in the document uses the
* total energy, but here I'm using the critical energy in kinetic energy,
* so I should check to see if I need to convert both. */
b = log(1 + T/MUON_CRITICAL_ENERGY)/range;
a = MUON_CRITICAL_ENERGY*b;
E = T + a*(1-exp(b*x))/b;
if (E < 0) return 0;
return E;
}
double get_dEdx(double T, double rho)
{
/* Returns the approximate dE/dx for a muon in water with kinetic energy
* `T`.
*
* `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. */
if (!initialized) {
if (init()) {
exit(1);
}
}
return gsl_spline_eval(spline_dEdx, T, acc_dEdx)/rho;
}
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