# 10th International Workshop on Ring Imaging Cherenkov Detectors

29 July 2018 to 4 August 2018
Europe/Moscow timezone

## Silica aerogel radiator for the HELIX RICH system

3 Aug 2018, 12:15
25m

Leninsky Prospekt, 32а Moscow 119071 Russian Federation
oral presentation [20+5 min] Technological aspects and applications of Cherenkov detectors

### Speaker

Makoto Tabata (Chiba University)

### Description

We have been developing silica aerogels for use as RICH radiators used in the HELIX (High-Energy Light Isotope eXperiment) spectrometer. The HELIX program is a balloon-borne cosmic-ray experiment designed to measure the mass of light cosmic-ray isotopes (in particular, those of beryllium). The main objective is to explore the propagation mechanism of cosmic rays by measuring the relative abundances of key light cosmic-ray isotopes. The first flight is scheduled during NASA's 2019/20 Antarctic long-duration balloon campaign.
The HELIX instrument consists of a 1-T superconducting magnet, a gas drift chamber, time-of-flight counters, and an aerogel RICH system. The HELIX RICH is used for measuring the velocity of cosmic-ray isotopes in an energy range from 1 to 3 GeV/nuc. The system is a proximity-focusing RICH with an expansion length of 50 cm, and a focal-plane composed of a silicon-photomultiplier module array with a pixel size of 6 mm. Hydrophobic aerogels with a refractive index, n of 1.15 were chosen as the radiators. The requirements for the aerogels include tile dimensions of 10 $\times$ 10 $\times$ 1 cm and refractive index and thickness uniformities of ~1% across the tile for the precise determination of the particle velocity. The dimensions of the radiator module are 60 $\times$ 60 cm; thus, a total of 36 tiles are needed.
Developing highly transparent aerogels with an ultrahigh index exceeding 1.10 without cracking is a serious challenge. In late 2016, we began the experimental fabrication of aerogels specific for HELIX. We determined that the production of n = 1.15 tiles is feasible using the pin-drying technology. In early 2018, we succeeded in prototyping highly transparent (a transmittance of ~73% for 400-nm wavelength) aerogels close to the flight-qualified radiators. We have begun the mass production of 92 tiles as candidates for the flight aerogels at the end of March 2018. Here, progress in the development and mass production of high optical quality aerogels is presented.

### Primary author

Makoto Tabata (Chiba University)

### Co-authors

Patrick Allison (Ohio State University) James J. Beatty (Ohio State University) Stephane Coutu (Penn State University) Mark Gebhard (Indiana University) Noah Green (University of Michigan) David Hanna (McGill University) Brandon Kunkler (Indiana University) Mike Lang (Indiana University) Isaac Mognet (Penn State University) Dietrich Müller (University of Chicago) James Musser (Indiana University) Scott Nutter (Northern Kentucky University) Nahee Park (University of Chicago) Michael Schubnell (University of Michigan) Gregory Tarlé (University of Michigan) Andrew Tomasch (University of Michigan) Gerard Visser (Indiana University) Scott P. Wakely (University of Chicago) Ian Wisher (University of Chicago)

### Presentation Materials

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