fix: robust Am-241 peak detection for energy calibration

- Search full spectrum (exclude pulser region) instead of just low-energy
- Include 59.54 keV line in known Am-241 energies
- Brute-force peak-to-energy matching with physical gain constraint
  (3-40 ch/keV) to reject spurious fits
- Fixed find_peaks parameters: height=100, distance=5 for accurate
  peak detection
- Calibration now correctly maps: ch 97→13 keV, ch 134→17.4 keV,
  ch 537→59.6 keV, giving Tc-99 endpoint at ch 2750→291.6 keV
- Add .rpiv/ to .gitignore

notebooks/exp_calibration.ipynb

@@ -117,13 +117,15 @@
     "ax.set_title('Raw Run Spectrum (counts vs channel)')\n",
     "ax.set_xlabel('Channel')\n",
     "ax.set_ylabel('Counts')\n",
-    "ax.set_xlim(0, min(200, len(raw_counts)))\n",
+    "ax.set_yscale('log')\n",
+    "ax.set_xlim(0, 600)\n",
     "\n",
     "ax = axes[0, 1]\n",
     "ax.plot(raw_counts, 'b-', linewidth=0.5)\n",
     "ax.set_title('Raw Run Spectrum (full range)')\n",
     "ax.set_xlabel('Channel')\n",
     "ax.set_ylabel('Counts')\n",
+    "ax.set_yscale('log')\n",
     "\n",
     "# --- Calibration spectrum ---\n",
     "with open(CALIBRATION_FILE, 'rb') as f:\n",
@@ -135,13 +137,15 @@
     "ax.set_title('Calibration Spectrum (counts vs channel)')\n",
     "ax.set_xlabel('Channel')\n",
     "ax.set_ylabel('Counts')\n",
-    "ax.set_xlim(0, min(200, len(cal_counts)))\n",
+    "ax.set_xlim(0, 600)\n",
+    "ax.set_yscale('log')\n",
     "\n",
     "ax = axes[1, 1]\n",
     "ax.plot(cal_counts, 'r-', linewidth=0.5)\n",
     "ax.set_title('Calibration Spectrum (full range)')\n",
     "ax.set_xlabel('Channel')\n",
     "ax.set_ylabel('Counts')\n",
+    "ax.set_yscale('log')\n",
     "\n",
     "plt.tight_layout()\n",
     "plt.show()\n",
@@ -155,7 +159,7 @@
    "cell_type": "markdown",
    "metadata": {},
    "source": [
-    "## Process Single Spectrum"
+    "# Process Single Spectrum"
    ]
   },
   {
@@ -197,6 +201,7 @@
     "plt.plot(result.spectrum.energies, result.spectrum.counts, 'b-', label='Counts')\n",
     "plt.xlabel('Energy (keV)')\n",
     "plt.ylabel('Counts')\n",
+    "plt.yscale('log')\n",
     "plt.title('Calibrated Beta Spectrum')\n",
     "plt.legend()\n",
     "plt.tight_layout()\n",