KNI-MDL Seminar

The Faint Intergalactic Redshifted Emission Balloon: future UV observations of the circumgalactic medium, Dr. Erika T. Hamden, Caltech

The Faint Intergalactic Redshifted Emission Balloon (FIREBall-2) is a joint NASA/CNES collaboration that will launch in 2016. FIREBall-2 is a balloon-born ultraviolet (UV) multi-object spectrograph designed to detect faint emission from the circumgalactic medium (CGM) around low z galaxies. This emission is visible via a narrow atmospheric window (195-225 nm) accessible at balloon altitudes (40km). We present the current state of low redshift CGM observations, using both absorption line studies and simulations, as well as new results at higher redshift by our group at Caltech. FIREBall-2 will observe CGM emission in the UV for the first time and will serve as a test bed for new technology, including a photon-counting anti-reflection coated delta-doped electron multiplying CCD (EMCCD). FIREBall-2 is expected to launch in the spring of 2016. Characterization and minimization of detector noise from an e2v CCD201-20 is ongoing. We will examine the overall performance goals for photon counting, describe improvements over current detector technology, and estimate the expected detection limits for our flight in 2016.

High Performance Silicon Detectors for UV/Visible/NIR Applications, Dr. April D. Jewell, JPL

With the abundance of lines in ultraviolet, UV spectroscopy is used in almost every planetary mission and is planned for astrophysics Explorer missions. The measurements are photon starved and detector limited. Delta-doped arrays, invented at JPL, achieve 100% internal QE from the UV through the visible. External losses due to reflection (~70% in some UV regions) can be mitigated with antireflection (AR) coatings. Using atomic layer deposition (ALD) thin-film optical filters are incorporated with existing detector technologies. ALD offers nanometer-scale control over film thickness and interface quality, allowing for precision growth of multilayer films. Here we present an overview of the detector for the upcoming Faint Intergalactic Red-shifted Emission Balloon (FIREBall-2) experiment, with a particular focus on the development of device-integrated optical coatings and detector quantum efficiency (QE). FIREBall-2 is designed to measure emission from the strong resonance lines of HI, OVI, and CIV, all red-shifted to 195-225 nm window; its detector is a delta-doped electron multiplying charge-coupled device (EM-CCD). JPL procured fully fabricated wafers, which were then modified for back-illumination, and delta doped to achieve UV sensitivity using JPL-developed processes. Several AR coatings, including single and multi-layer designs, were tested for FIREBall-2. QE measurements match modeled transmittance behavior remarkably well, showing absolute QE>80% within the target wavelength range. Also under development are ALD coatings to enhance QE for a variety of spectral regions throughout the UV (90-320) and visible (320-1000 nm), both for space-based imaging and spectroscopy as well as for ground-based telescopes.