VERITAS Upgrade OverviewVERITAS Upgrade Overview

Rene Ong (UCLA)

Jamie Holder (Delaware)

VERITAS Operations Review, Tucson, December, 2009

VERITAS StatusVERITAS Status

• In summer 2009 VERITAS T1 was relocatedIn summer 2009, VERITAS T1 was relocated.• A new mirror alignment system (McGill) also significantly improved the optical performance.• VERITAS is currently the most sensitive TeV Observatory in the worldVERITAS is currently the most sensitive TeV Observatory in the world.

The CompetitionThe Competition

H.E.S.S Phase II

HESS Phase II:• A single large (600m2 mirror area) telescope to be located at area) telescope to be located at the center of the array.• Camera is complete.• Telescope structure still under Telescope structure still under construction in Namibia.

MAGIC II MAGIC II:• MAGIC have installed a second 17m diameter telescope 80m from MAGIC I.• Stereo observations began this summer.• No report on sensitivity yet.

VERITAS Upgrade Overview

• Many options were considered over a series of meetings• Key goals:

•reduce energy threshold and improve sensitivity•reduce energy threshold and improve sensitivity.

• These goals impact essentially all science programs, and b t il hi d t th t it b can be most easily achieved at the current site by: • Increasing the photon collection efficiency • Upgrading the triggerpg g gg

• Additionally, we plan to add a unique scientific capability, at low cost by instrumenting the central pixel of each at low cost, by instrumenting the central pixel of each telescope with fast readout and continuous digitization.

Why Improve Sensitivity?• For a pointed instrument such as VERITAS, with a limited duty cycle,

d h h l F leven a modest sensitivity improvement is worthwhile. For example:

• M82 “Nature” result required 2 seasons, and 150 hoursseasons, and 150 hours• The new configuration reduces this to ~90 hours• The proposed upgrade reduces this to The proposed upgrade reduces this to ~60 hours: easily achievable in a single season.

• The VERITAS Catalog now contains 27 sources.• Many require follow-up y q pobservations.• New sources are being added (>1/month since the (summer).• VERITAS time is precious!

VERITAS Catalog

Why Lower the Threshold?• Lowering the energy thresholds impacts many areas of VERITAS science:

C l t b db d t ith F i• Complete broadband source spectra with Fermi.• Increased energy range for dark matter searches.• Energy dependent morphology studies of extended sources.

• Fermi shows that delayed high energy emission from GRBs is

k

• The gamma-ray horizon is not as restrictive as once thought - VERITAS continues to push the distance record ( E )common – up to ksecs. (3C66A, 1ES 0502+675).• A lower threshold accesses more distant sources, and provides a more sensitive probe of the EBLsensitive probe of the EBL.

1ES 0502+675z = 0.341

GRB 080916C

Increasing the photon collection Efficiency: High QE PMTs

• ‘Super Bialkali’ PMTs offer 50% improved photon collection efficiency.• Equivalent to increasing the mirror area by the same factor. • Dramatic improvement in the low-energy response.p gy p• Sensitivity improvement also expected (~30% reduction in the observing time required to detect a source).

High QE PMTs• Three potential Hamamatsu replacement tubes identified:

• R10408-01HQE: Used for MAGIC II. Low gain (6 stages).• R9800-100: Best match in physical dimensions and gain (8 stages).• R10560-100: UV glass version of the R9800. g

• Samples of R10408 and R9800 are in hand. Testing is underway at Purdue and Wash U. One R10408 pixel also installed in T4.

Preliminary Purdue resultsR10408-01HQE

y

High QE PMTs• Three potential Hamamatsu replacement tubes identified:

• R10408-01HQE: Used for MAGIC II. Low gain (6 stages).• R9800-100: Best match in physical dimensions and gain (8 stages)• R10560-100: UV glass version of the R9800 g

• Samples of R10408 and R9800 are in hand. Testing is underway at Purdue and Wash U. One R10408 pixel also installed in T4.

Preliminary Wash U resultsR10408-01HQE

Preliminary Wash U results

High QE PMTs• Practicalities:

• PMT cost ~ $1.2M• Delivery timescales 12 months (R10408) – 18 months (R10560)

• Also requires q• New pre-amplifiers• Pixel assembly• Camera integrationCamera integration• New light cones

• Total cost ~$2.0M

Trigger Upgrade• Each PMT signal channel has programmable Discriminators (CFDs)• CFD output sent to programmable pattern selection trigger (L2)

• any 3 adjacentPMTs in a camera within ~7ns• A valid trigger is transmitted to a central array trigger (L3), which

f h l h d i l i idcorrects for path length and triggers on telescope coincidence•any 2 out of 4 telescopes within 50ns

• Trigger rate ~ 250 Hz

Noise Tri ers

Individual telescopes

Triggers

telescopes

Array Cosmic Ray triggerstriggers

Trigger Upgrade• Current L2 system is CAMAC-based,

RAM l k bl h k uses RAM memory lookup tables to check for valid patterns (e.g. any 3 adjacent pixels).• The design is old technology slow and The design is old technology, slow, and provides little diagnostic monitoring.• Iowa State/Argonne have developed and field-tested a fast FPGA based L2

Test of the prototype ISU/ANL trigger ( on T4 (April 4, 2009).

trigger system.• This system will allow to reduce the coincidence gate width by a factor of two provides real time diagnostic two, provides real-time diagnostic monitoring and channel-channel time skew adjustment.• The system also allows a fast yparameterization of ‘hit’ pixels.• This information can be used as input for a future geometrical array trigger providing gamma hadron discrimination at providing gamma-hadron discrimination at the hardware level (e.g. with parallaxwidth parameter). Bias curves obtained on T4 simultaneously with

the VERITAS trigger and the ISU/ANL trigger.

Trigger Upgrade• Current L2 system is CAMAC-based,

RAM l k bl h k

γ-ray proton/NSB

uses RAM memory lookup tables to check for valid patterns (e.g. any 3 adjacent pixels).• The design is old technology slow and The design is old technology, slow, and provides little diagnostic monitoring.• Iowa State/Argonne have developed and field-tested a fast FPGA based L2 trigger system.• This system will allow to reduce the coincidence gate width by a factor of two provides real time diagnostic two, provides real-time diagnostic monitoring and channel-channel time skew adjustment.• The system also allows a fast yparameterization of ‘hit’ pixels• This information can be used as input for a future geometrical array trigger providing gamma hadron discrimination at

Rejectbackground

providing gamma-hadron discrimination at the hardware level (e.g. with parallaxwidth parameter).

Trigger Upgrade

• Simulations indicate significant reductions in background, providing Simulations indicate significant reductions in background, providing lower energy threshold.• Improved diagnostics, maintenance and support are also important• Total cost ~$300kTotal cost $300k.

Fast Optical Observations• ACTS are arrays of >10 m class optical telescopes, with relatively crude optics and very fast photon detectorsand very fast photon detectors.• This provides access to a largely unexplored parameter space, to study fast optical transient events, and perform optical intensity interferometry.• Modern off-the-shelf digitizers and high speed disks allow storage of a complete g g p g pnight’s waveforms for a single PMT in each telescope which can then be analysed and correlated offline.• The cost is ~$240k, and will allow useful scientific observations during bright

li htmoonlight.

National Instruments 200MS/s PXIe digitizer

Status of proposals

• MRI-R2 proposal submitted to NSF through the University of MRI R proposal submitted to NSF through the University of Utah, with $544k matching funds from Utah.• Regular NSF proposal submitted through SAO.

Th l l d d h VER T • This also includes a component to upgrade the VERITAS mirror coating facility:

• hardware cost of only $38k.• constant high reflectivity is a significant advantage over e.g. HESS,

whose mirrors have degraded to ~60%• the existing 25 year old pump is a “single point of failure”, whose the existing 25 year old pump is a single point of failure , whose

replacement could take many months • The upgrade proposal was also submitted to DoE.

• VERITAS Upgrade program was presented as an RFI to the ASTRO2010 decadal review, and to the DoE PASAG. • The PASAG report recommends support for the upgrade under all funding scenarios.

Upgrade Project Management(regular NSF proposal)

Summary

• The VERITAS collaboration plan to continue to upgrade the The VERITAS collaboration plan to continue to upgrade the observatory over the coming years.• Improved sensitivity, and a lower energy threshold will have the broadest impact on all VERITAS science goalsbroadest impact on all VERITAS science goals.• These can best be achieved at the current site by improving the camera photon collection efficiency, and by upgrading the trigger• Technological developments (High QE PMTs and fast FPGAs) allow these goals to be met. • An optical monitoring/ intensity interferometry upgrade provides • An optical monitoring/ intensity interferometry upgrade provides a novel way to increase the science yield from the observatory, at modest cost.

Backup Slides

Trigger Development• Hardware produced (I/O, L1.5, L2) and tested on one VERITAS telescope

• VERITAS camera processed in three 192-pixel L1.5 boards for coincidences and merged in L2

• Bias curve shows lower inflection point due to improved efficiency in rejecting NSB (slightlyBias curve shows lower inflection point due to improved efficiency in rejecting NSB (slightly faster coincidence requirement)

• 20% higher cosmic-ray rate: larger trigger field-of-view, better timing alignment

Bias curves obtained on T4 simultaneously with the VERITAS trigger and the topological trigger (TT). The coincidence gate of the TT was slightly shorter than the standard trigger.

Test of the prototype topological trigger (TT) on T4 (April 4, 2009).

Channel Timing Alignment

•Compensate different Would Loose pdelay times (HV and cables)•Range: 0 to 5 ns•Precision: 50 ps•Measured with 30 min

Would Loose150 pixelsWithout Alignmentat 3 ns Gate width

laser run at nominal HV•Intend to improve to better than 1 ns FWHM

•Working underway to understand delays of ~10 outliers • Could fix with additional 6ns from FADC-output module

Not shown: ~25 dead CFD channels in T4

Background Suppression with Topological Array Trigger (L4)

γ-ray proton • Calculate 1st moment of image in each camera• Use stereo view from multiple telescopes to project image back into the sky• Identify γ-ray images by tight correlation of projection• Do this in real time (10 MHz at L2, 10 kHz

Parallaxwidth ≡<d >

at L4)

di

Parallaxwidth ≡<di>

Rejectbackgroundbackground

• Q-factor ~1.5• Method verified with VERITAS data!