CREAM

CREAM [NASA]

The CREAM (Cosmic Ray Energetics And Mass), also known as ISS-CREAM, is a suite of particle detectors to measure TeV cosmic-ray elemental spectra from protons to iron nuclei over a wide energy range. The goal is to extend direct measurements of cosmic-ray composition to the highest energies practical, and thereby have enough overlap with ground based indirect measurements to answer questions on cosmic-ray origin, acceleration and propagation.

CREAM was originally a balloon borne exoeriment, which was flown successfully for about 161 days in six flights over Antarctica to measure elemental spectra of Z = 1–26 nuclei over the energy range 1010 to >1014 eV.

The CREAM instrument consists of a set of complementary and redundant particle detectors. An ionization calorimeter determines the energy of the cosmic ray particles, provide tracking, and event trigger. Silicon charge detectors provide precise charge measurements. Top/bottom counting detectors provide shower profiles for electron/hadron separation. The BSD (Boronated Scintillator Detector) provides additional electron/hadron discrimination using thermal neutrons produced by particles that interact within the calorimeter.

The objectives of CREAM are

• to determine how the observed spectral differences of protons and heavier nuclei evolve at higher energies approaching the knee;
• to be capable of measuring potential changes in the spectra of secondary nuclei resulting from interactions of primary cosmic rays with the interstellar medium;
• to conduct a sensitive search for spectral features, such as a bend in proton and helium spectra; and
• to measure electrons with sufficient accuracy and statistics to determine whether or not a nearby cosmic-ray source exists.

It will also contribute indirectly to the dark matter search by measuring electrons in addition to nuclei at energies beyond where current direct measurements exist.

CREAM will be transported by the Dragon CRS-12 transporter to the ISS in August 2017. CREAM is installed on the JEF (JEM-EF) exposed facility of the Japanese JEM module to allow zenith viewing. The CREAM investigation is designed to operate on the JEM-EF for 3 years.