Introduction and EGADS (A03) Status Mark Vagins Kavli IPMU, UTokyo Multi-Messenger Kakenhi Bi-Monthly Meeting Kashiwa April 15, 2014

Let’s start at the very beginning (a very good place to start): Wolfgang Pauli’s famous 1930 letter in which the neutrino – called the “neutron” until Fermi renamed it in 1934 – was first proposed.

Dear Radioactive Ladies and Gentlemen, …I have hit upon a desperate remedy to save the…law of conservation of energy…there could exist…electrically neutral particles, that I wish to call neutrons, which have spin 1/2 and obey the exclusion principle and which further differ from light quanta in that they do not travel with the velocity of light. I agree that my remedy could seem incredible… But only the one who dare can win… …dear radioactive people, look and judge. Your humble servant W. Pauli

Pauli thought this idea was so crazy he didn’t publish it! Twenty years later, along came the first really serious proposal to detect neutrinos. It was suggested by a 32 year old named Frederick Reines, a protégé of an even younger (well, 63 days younger) Richard Feynman. However, this proposal probably isn’t the experiment you’re thinking of right now.

This sketch is from Fred’s 1st proposal. It was not approved!

It took Fred and his team several more years and a few approved experiments until they finally managed to detect neutrinos. These pictures are from an unsuccessful experiment at the Hanford reactor in 1953.

The first certain neutrino detection At last, success! The first certain neutrino detection took place in 1956 at the Savannah River nuclear reactor in South Carolina. 39 long years later, Reines would finally be given the 1995 Nobel Prize in physics for this discovery.

1.8 MeV threshold

Ring-Imaging Water Cherenkov Detector Relativistic charged particles traveling through water make rings of light on the inner wall of the detector. The rings are then imaged by photomultiplier tubes. Dominant neutrino detection technology from 1981 to the present day: IMB/Kamiokande/Super-K/SNO/Hyper-K

A core-collapse supernova is a nearly perfect “neutrino bomb”. It releases >98% of its huge energy as neutrinos. In 1987, we saw the evidence firsthand... Kamiokande

Kamiokande IMB Baksan

Event Displays of Actual Neutrinos from SN1987A IMB (in USA) Kamiokande (in Japan) Event Displays of Actual Neutrinos from SN1987A

UTokyo professor Masatoshi Koshiba ultimately received the 2002 Nobel Prize in physics for observing the neutrinos from SN1987A with Kamiokande.

Kamiokande = Kamioka Nucleon Decay Experiment Super-Kamiokande = Super Kamioka Neutrino Detection Experiment Neutrinos – atmospheric, solar, and supernova – were the stars of the show after 1987!

Elastic Scattering (~3%  directional) Inverse Beta Decay (~80% of events dominant, but challenging to uniquely identify) Elastic Scattering (~3%  directional) Possibility 1: 10% or less n+p→d + g n g ne 2.2 MeV g-ray p p 2.2 MeV gammas are difficult to detect and, more importantly, difficult to distinguish from backgrounds. Gd e+ g Possibility 2: 90% or more n+Gd →~8MeV g DT = ~30 msec

Inverse Beta Decay with Gadolinium [Beacom and Vagins, Phys. Rev. Lett., 93:171101, 2004] Possibility 1: 10% or less n+p→d + g n g ne 2.2 MeV g-ray p p Gd e+ g Possibility 2: 90% or more n+Gd →~8MeV g DT = ~30 msec Positron and gamma ray vertices are within ~50 cm ne can be positively identified by delayed coincidence. Even a single coincident pair + GW  Supernova!

If so, this is the likely future of all water Cherenkov detectors. EGADS University of Tokyo (ICRR and IPMU), University of California (UCI), and Okayama University have built a dedicated 200-ton Gd demonstrator project: EGADS – Evaluating Gadolinium’s Action on Detector Systems. Super-Kamiokande EGADS Facility Super-K Water system EGADS Hall (2500 m^3) 12/2009 2/2010 6/2010 12/2010 By the middle of this year EGADS will have shown conclusively whether or not gadolinium loading is safe and effective. If so, this is the likely future of all water Cherenkov detectors.

The EGADS Detector Facility @ Kamioka; November 28th, 2012 One Kilometer Underground Main 200-ton Water Tank with 227 50-cm PMT’s + 13 HK tubes (PMT’s installed in summer of 2013) Membrane Flushing System Resin-based Gadolinium Removal System 15-ton Gadolinium Pre-treatment Mixing Tank Selective Water+Gd Filtration System The EGADS Detector Facility @ Kamioka; November 28th, 2012

Gd loading of the 200-ton tank Feb. 6th, 2013: Inject first 30 kg of Gd2(SO4)3*8H2O Feb. 13th: Inject another 30 kg (60 kg total) March 6th: Inject 29.4 kg (89.4 kg total) March 20th/21st: Inject 60 kg (149.4 kg total) April 1st/2nd: Inject 124.6 kg (274 kg total) April 16th 20th: Inject 126 kg (400 kg total) World record: Largest single quantity of gadolinium in solution!

SK-III and SK-IV Ultrapure Water = 74.7% - 82.1% @ 15 m 30 kg of Gd2(SO4)3*8H2O  35% n capture on Gd 60 kg of Gd2(SO4)3*8H2O  52% n capture on Gd 89.4 kg of Gd2(SO4)3*8H2O  62% on Gd 149.4 kg of Gd2(SO4)3*8H2O  73% on Gd 274 kg of Gd2(SO4)3*8H2O  83% on Gd 400 kg of Gd2(SO4)3*8H2O  88% on Gd Light remaining @ 15 meters (characteristic distance in Super-K)  gadolinium sulfate’s light absorption is acceptable 

We then drained the tank to prepare for PMT installation. Looking down into the EGADS tank after four months of gadolinium exposure. No rust, no problems!

EGADS PMT installation; August 2013

Working Inside the EGADS Tank; August 2013

Looking Down Into the Completed EGADS Detector; August 2013 Insert: Event Display of a Downward-Going Cosmic Ray Muon

The first scoop of gadolinium sulfate for the EGADS detector! March 26th, 2014: The first scoop of gadolinium sulfate for the EGADS detector!

Gd loading of the 200-ton detector March 26th, 2014: Inject first 30 kg of Gd2(SO4)3*8H2O April 10th: Inject another 30 kg (60 kg total) Through calibration and transparency studies we are currently working to understand the effects of adding Gd to the running (24/7) detector. As we did with the empty tank last year, the plan is to add more Gd in stages as these studies are completed and the detector response is understood.

100% Captures on Gd 80% 60% 40% 20% 0% Gd in Water Thermal neutron capture cross section (barns) Gd = 49700 S = 0.53 H = 0.33 O = 0.0002 Captures on Gd Final Target: 400 kg  88% 60 kg  52% 30 kg of Gd2(SO4)3 8H2O in 200 tons  35% capture on gadolinium Gd in Water 0.0001% 0.001% 0.01% 0.1% 1%

EGADS EGADS valuating adolinium’s ction on etector ystems mploying We expect all R&D to be completed during the first half of 2014. But what happens to our major underground facility after that? EGADS valuating adolinium’s ction on etector ystems EGADS mploying adolinium to utonomously etect upernovas This multimessenger kakenhi is supporting the conversion (via upgraded electronics, realtime event reconstruction, etc) of EGADS from an R&D facility into the world’s most advanced water-based supernova neutrino detector.

Special features of SN neutrinos and GW’s Provide image of core collapse itself (identical t=0) Only supernova messengers which travel without attenuation to Earth (dust does not affect signal) Guaranteed full-galaxy coverage What is required for maximum SN n information? Full sensitivity to very nearby explosions (close gap in Super-Kamiokande’s galactic SN n coverage) Deconvolution of neutrino flavors via neutron tags Ultrafast alert generation to aid other observations

An EGADS timeline: 2009 2010 2011 2012 2013 2014 2015 2016 2017 R&D Project Approved Hall E Excavation Build 200-ton Tank Install Water Systems 15-/200-t Pure Water Runs 15-ton Tank Gd Runs 200-ton Tank Pure Water Run w/o PMTs 200-ton Tank Gd Run w/o PMTs 200-ton Tank PMT Installation 200-ton Tank Pure Water Data-taking Run 200-ton Tank Gd Data-taking Run (March 26th) ATM  QBEE Electronics Upgrade Full Galaxy Supernova Sensitivity Fully Automated Instant Supernova Alert Capability

~90,000 n events from Betelgeuse Our target: send out an announcement within one second of the SN neutrino burst’s arrival in EGADS! ~90,000 n events from Betelgeuse ~40 n events from G.C.

 We will let you know the light is on its way!  In 2015 we expect to be ready to detect supernova neutrinos from anywhere in our galaxy, and send an immediate alert to the rest of this Kakenhi’s members and their facilities around the world.  We will let you know the light is on its way! 