  The Serappis (SEarch for RAre PP-neutrinos In Scintillator) project aims at a
precision measurement of the flux of solar $pp$ neutrinos on the few-percent
level. Such a measurement will be a relevant contribution to the study of solar
neutrino oscillation parameters and a sensitive test of the solar luminosity
constraint. The concept of Serappis relies on a small organic liquid
scintillator detector ($\sim$20 m$^3$) with excellent energy resolution
($\sim$2.5 % at 1 MeV), low internal background and sufficient shielding from
surrounding radioactivity. This can be achieved by a minor upgrade of the
OSIRIS facility at the site of the JUNO neutrino experiment in southern China.
To go substantially beyond current accuracy levels for the $pp$ flux, an
organic scintillator with ultra-low $^{14}$C levels (below $10^{-18}$) is
required. The existing OSIRIS detector and JUNO infrastructure will be
instrumental in identifying suitable scintillator materials, offering a unique
chance for a low-budget high-precision measurement of a fundamental property of
our Sun that will be otherwise hard to access.
