diff --git a/CRV/CrvCalibration.C b/CRV/CrvCalibration.C
index 66a0fe0..50ab44f 100644
--- a/CRV/CrvCalibration.C
+++ b/CRV/CrvCalibration.C
@@ -1,3 +1,13 @@
+const double fitRangeStart=0.8;
+const double fitRangeEnd=1.2;
+const int    minHistEntries=100;
+const int    spectrumNPeaks=6;
+const double spectrumPeakSigma=4.0;
+const double spectrumPeakThreshold=0.01;
+const double peakRatioTolerance=0.1;
+
+bool FindSPEpeak(TH1F *hist, TSpectrum &spectrum, double &SPEpeak);
+
 void CrvCalibration(const std::string &inputFileName, const std::string &outputFileName)
 {
     TFile *inputFile = TFile::Open(inputFileName.c_str(),"update");
@@ -14,7 +24,8 @@ void CrvCalibration(const std::string &inputFileName, const std::string &outputF
       pedestals[channel]=pedestal;
     }
 
-    TF1 funcCalib("f0", "gaus");
+    TF1 funcCalib("SPEpeak", "gaus");
+    TSpectrum spectrum(spectrumNPeaks); //any value of 3 or less results in a "Peak buffer full" warning.
 
     std::ofstream outputFile;
     outputFile.open(outputFileName);
@@ -33,33 +44,21 @@ void CrvCalibration(const std::string &inputFileName, const std::string &outputF
         if(i==1) hist=(TH1F*)gDirectory->FindObjectAny(Form("crvCalibrationHistPulseArea_%zu",channel));
         else hist=(TH1F*)gDirectory->FindObjectAny(Form("crvCalibrationHistPulseHeight_%zu",channel));
 
-        if(hist->GetEntries()<100) //not enough data
-        {
-          calibValue[i]=-1;
-          continue;
-        }
-
-/*
-        int n=hist->GetNbinsX();
-        double overflow=hist->GetBinContent(0)+hist->GetBinContent(n+1);
-        if(overflow/((double)hist->GetEntries())>0.1) //too much underflow/overflow. something may be wrong.
+        double peakCalib=0;
+        if(!FindSPEpeak(hist, spectrum, peakCalib))
         {
           calibValue[i]=-1;
           continue;
         }
-*/
 
-        int maxbinCalib = hist->GetMaximumBin();
-        double peakCalib = hist->GetBinCenter(maxbinCalib);
-//FIXME        funcCalib.SetRange(peakCalib*0.8,peakCalib*1.2);
-        funcCalib.SetRange(peakCalib*0.7,peakCalib*1.3);
-        if(hist->FindBin(peakCalib*0.7)==hist->FindBin(peakCalib*1.3))
+        funcCalib.SetRange(peakCalib*fitRangeStart,peakCalib*fitRangeEnd);
+        if(hist->FindBin(peakCalib*fitRangeStart)==hist->FindBin(peakCalib*fitRangeEnd)) //fit range start/end are in the same bin
         {
           calibValue[i]=-1;
           continue;
         }
         funcCalib.SetParameter(1,peakCalib);
-        hist->Fit(&funcCalib, "0QR");
+        hist->Fit(&funcCalib, "QR");
         calibValue[i]=funcCalib.GetParameter(1);
       }
 
@@ -91,3 +90,28 @@ void CrvCalibration(const std::string &inputFileName, const std::string &outputF
     outputFile.close();
     inputFile->Close();
 }
+
+bool FindSPEpeak(TH1F *hist, TSpectrum &spectrum, double &SPEpeak)
+{
+    if(hist->GetEntries()<minHistEntries) return false; //not enough data
+
+    int nPeaks = spectrum.Search(hist,spectrumPeakSigma,"nodraw",spectrumPeakThreshold);
+    if(nPeaks==0) return false;
+
+    //peaks are not returned sorted
+    double *peaksX = spectrum.GetPositionX();
+    double *peaksY = spectrum.GetPositionY();
+    std::vector<std::pair<double,double> > peaks;
+    for(int iPeak=0; iPeak<nPeaks; ++iPeak) peaks.emplace_back(peaksX[iPeak],peaksY[iPeak]);
+    std::sort(peaks.begin(),peaks.end(), [](const std::pair<double,double> &a, const std::pair<double,double> &b) {return a.first<b.first;});
+
+    int peakToUse=0;
+    if(nPeaks>1 && peaks[0].first>0)   //if more than one peak is found, the first peak could be due to baseline fluctuations
+    {
+      if(fabs(peaks[1].first/peaks[0].first-2.0)>peakRatioTolerance) peakToUse=1; //2nd peak is not twice the 1st peak, so the 1st peak is not the SPE peak
+                                                                                  //assume that the 2nd peak is the SPE peak
+                                                                                  //we have never seen that the 3rd peak was the SPE peak - no need to test it
+    }
+    SPEpeak = peaks[peakToUse].first;
+    return true;
+}
diff --git a/CRV/CrvPass1_extracted.fcl b/CRV/CrvPass1_extracted.fcl
index e56df3a..373dec4 100644
--- a/CRV/CrvPass1_extracted.fcl
+++ b/CRV/CrvPass1_extracted.fcl
@@ -84,6 +84,7 @@ physics.producers.CrvCoincidenceClusterFinder.sectorConfig:
           maxSlopeDifference : 4
           coincidenceLayers : 3
           minClusterPEs : 0
+          initialClusterMaxDistance : 250
         },
         {
           CRVSector : "T1"
@@ -97,6 +98,7 @@ physics.producers.CrvCoincidenceClusterFinder.sectorConfig:
           maxSlopeDifference : 4
           coincidenceLayers : 3
           minClusterPEs : 0
+          initialClusterMaxDistance : 250
         },
         {
           CRVSector : "T2"
@@ -110,6 +112,7 @@ physics.producers.CrvCoincidenceClusterFinder.sectorConfig:
           maxSlopeDifference : 4
           coincidenceLayers : 3
           minClusterPEs : 0
+          initialClusterMaxDistance : 250
         }
       ]