The energy spectrum and primary composition of cosmic rays with energy between 3 \times 10 ^ { 14 } and 3 \times 10 ^ { 16 } \mathrm { eV } have been studied using the CASA-BLANCA detector .
CASA consisted of 957 surface scintillation stations ; BLANCA consisted of 144 angle-integrating Cherenkov light detectors located at the same site .
CASA measured the charged particle distribution of air showers , while BLANCA measured the lateral distribution of Cherenkov light .
The data are interpreted using the predictions of the CORSIKA air shower simulation coupled with four different hadronic interaction codes .

The differential flux of cosmic rays measured by BLANCA exhibits a knee in the range of 2–3 PeV with a width of approximately 0.5 decades in primary energy .
The power law indices of the differential flux below and above the knee are -2.72 \pm 0.02 and -2.95 \pm 0.02 , respectively .

We present our data both as a mean depth of shower maximum and as a mean nuclear mass .
A multi-component fit using four elemental species suggests the same composition trends exhibited by the mean quantities , and also indicates that QGSJET and VENUS are the preferred hadronic interaction models .
We find that an initially mixed composition turns lighter between 1 and 3 PeV , and then becomes heavier with increasing energy above 3 PeV .