Operative prototypes


Since 2018, the main prototype for R&D within the NEXT experiment has been DEMO++.  Like its predecessor, NEXT-DEMO, DEMO++ is located at IFIC and keeps taking data so as to perform several tests for the future generation detectors of the experiment.

DEMO++ TPC and gas system

Non-operative prototypes

The main aim of the NEXT-DEMO and NEXT-DBDM prototypes built at IFIC and LBNL respectively, was demonstrating NEXT energy resolution at reasonably high energies (e.g, using positron annihilation 511 keV gamma rays, Cs-137 660 keV gamma rays and Co-60 1.1 MeV gamma rays).


The IFIC NEXT-DEMO chamber was a large prototype of the baseline design for NEXT presented in the LOI.

It was an asymmetric SOFT (Separated-Optimized Function for Tracking) TPC, with SiPMs (coated with a wavelength shifter) in the anode and an array of pressure resistant photomultipliers in the cathode. The detector was housed in a 60cm long cylindrical chamber and has an hexagonal fiducial region of 30cm drift length and 16cm diagonal length.

The scintillation light was observed by 19 Hamamatsu R7378A PMTs (capable of withstanding a pressure of 10 bar) which provided the energy measurement and the t0 of the event. An electric field of up to 40 kV drifted the ionization charge to the electroluminescence region. Such a region was defined at the end of the drift region by two grids separated by 5mm with 3.5 kV/cm bar potential drop and was viewed by 248 SiPMs (model S10362- 11-025C). The SiPMs were placed in Daughter Boards (DB) that hold 16 SiPMs each and coated by a wavelength shifting TPB. The DB, in turn, fitted into a large Mother Board that channels the traffic of voltages and signals.

In order to improve light transport, the walls of the fiducial volume were made of polytetrafluoroethylene panels. A gas purification/re-circulation system was designed and built ad hoc.

NEXT-DEMO started operations in November 2010 and plenty of data have been collected.



The LBNL chamber was optimized to operate at the largest pressures considered for NEXT (20 bar). Its aim was to prove the energy resolution of NEXT, thus only an energy plane was constructed, using pressure-resistant PMTs but no tracking plane.

The gas system was fully operational and was routinely operated near its maximum rated pressure of 17 bar. Five conductive meshes established  the electric potentials in the TPC. The walls of the TPC were made of PTFE, bare, on the internal side to reflect UV photons and with conductive stripes (at intermediate potentials) on the outside to establish uniform electric field lines along the TPC main axis. The drift region was 8 cm long and the maximum HV on the dedicated feedthroughs was both +-20 kV. It then allowed one to measure the energy resolution for drift fields from 0 to 4 kV/cm while maintaining a constant EL gain.

The system was operational at LBNL since December 2010 and proved an energy resolution of 1.8% FWHM in the Cs-137 peak. Once extrapolated to the Qββ of Xe-136, it converts into ~0.9% FWHM.



Juan José Gómez Cadenas: jjgomezcadenas@dipc.org

Dave Nygren: nygren@uta.edu


NEXT Report from LSC - Oct 2021

NEXT-100 Technical Design Report

NEXT-100 Conceptual Design Report

Letter of Intent to LSC

Laboratorio Subterráneo de Canfranc (LSC)

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Starting from March 2013, NEXT is a Recognized Experiment at CERN!