  Large-amplitude, intermittent fluctuations are ubiquitous in the boundary
region of magnetically confined plasmas and lead to detrimental plasma-wall
interactions in the next-generation, high duty cycle fusion power experiments.
Using gas puff imaging data time series from the scrape-off layer in the
Alcator C-Mod device, it is here demonstrated that the large-amplitude
fluctuations can be described as a super-position of pulses with fixed shape
and constant duration. By applying a new deconvolution algorithm on the data
time series with a two-sided exponential pulse function, the arrival times and
amplitudes of the pulses can be estimated and the measurement time series can
be reconstructed with high accuracy. The pulse amplitudes are shown to follow
an exponential distribution. The waiting times between pulses are uncorrelated,
their distribution has an exponential tail, and the number of arrivals is a
linear function of time. This demonstrates that pulse arrivals follow a
homogeneous Poisson process. Identical statistical properties apply to both
ohmic and high confinement mode plasmas, clearly demonstrating universality of
the fluctuation statistics in the boundary region of Alcator C-Mod.
