Stability of the IMS Radionuclide Detector Network and Lessons - - PowerPoint PPT Presentation

Robert Lee, PhD, Maj, USAF Physics Department, USAF Academy Colorado Springs, CO Dan “Animal” Javorsek, PhD, Maj, USAF

Air Force Test Center Edwards AFB, CA

• D. Brent Morris, PhD, Col, USAF

Defense Threat Reduction Agency Ft Belvoir, VA

Stability of the IMS Radionuclide Detector Network …

… and Lessons Learned for Exotic Physics Searches

Overview

• Unusual oscillations in the RASA “check source”

photopeaks mimic reports of Decay Anomalies

• Dark Matter & Decay Anomaly Reports rely on

stability of a single detector

• RASA diagnostics and mult. geographic locations
• ffer unique capability to characterize oscillations
• Our analysis supports conventional explanation for
• scillations w/ implications for Anomaly Searches

IMS Check Source Data Is Used To Investigate Anomalous Decays

• Nuclear decay rates are constant?
• Many ways to perturb decay rates

– Chemical comp, pressure, E & B field…

• Literature shows many discrepancies

– Dark Matter Searches – Unexplained Periodicities (Neutrino Interactions?)

Background

t

e N dt dN t N

λ

λ

−

− = ≡ ) ( &

456 457 458 459 460 461 462 463 464 465

Vaninbrouckx Lagoutine Schrader Unterw eger Martin

Days

Measured Half-lives for 134Cs and 109Cd

134Cs 109Cd

751 752 753 754 755

Lagoutine Dietz Houtermans Unterw eger

Days

Background

• Nuclear decay rates are constant?
• Many ways to perturb decay rates

– Chemical composition, pressure, E & B field…

• Literature shows many discrepancies

– Unexplained periodicities – Dark Matter Search

t

e N dt dN t N

λ

λ

−

− = ≡ ) ( &

New Interest in Anomalies

25 Nuclides, 8 Detector Types: All show 1 yr-1 Periodicities

RASA Check Source Measurements

• Daily 10-15 min “check source” measurement
• Check source includes

– Cobalt (60Co) – Cesium (137Cs) – Europium (152Eu)

• Secondary Diagnostics

– Crystal Temperature – Room Temp / Humidity – Blower Speed – Power Consumption – Mostly unreported, but valuable! Small Count Rates, But Many Years Worth of Daily Measurements

Analysis Basics

Photopeaks utilized for the analysis were: Analysis includes: – Lomb-Scargle Power Spectrum – Shuffle Tests on Oscillations – Likliehood Analysis – Nelder-Mead Phase and Amplitude Fit – Frequency stability analysis w/ 1 yr window

Nuclide Decay Branching Ratio Analyzed Peak Energy [keV]

60Co

β- 100% 1173.2, 1332.5

137Cs

β- 100% 661.7

152Eu

ε 72.2% 122, 245, 964, 1086, 1112, 1408 β- 27.8% 344.3, 778.9

152Eu

β- 28% E.C. 72%

152Sm 152Gd

Annual Changes in 152Eu Branching Ratio Might Suggest New Physics

1) Determination of Residuals from Fit 2) Spectral Analysis 3) Significance Estimates

Analysis Methodology

10,000 shuffled trials

Year Net Count

Actual Data

Preliminary Analysis

• All stations certified at different times
• Calibrations are performed periodically

– Initially only 60Co and 137Cs, later 152Eu – Detector swaps limit check source continuity – As a result, the longest continuous data set between detector swap is used

Station Location Dates Analysis Dates USP 71 Sand Point, AK 1/1/07-4/5/13 4/17/09-4/5/13 USP 73 Palmer Station, Antarctica 3/3/06-4/5/13 6/22/09-4/5/13 USP 74 Ashland, KS 1/1/04-4/5/13 2/23/10-4/5/13 USP 76 Eielson AFB, AK 8/1/02-4/5/13 3/21/07-4/5/13

Daily RASA Operations & Diagnostics Provide a Unique Dataset

USP 73 – Palmer Station, Antarctica

Search for Annual Oscillations

Nuclide Energy Freq Power Amp Phase [φ φ φ φ] Shuffle Prob [%] Eu 121.8 0.98±0.22 4.2 0.0019

• 10.2±15.8

3.7 Eu 244.7 1.14±0.14 1.5 0.0020 4.0±15.4 49 Eu 344.3 0.82±0.27 2.5 0.0014 35.3±15.6 22.7 Cs 661.7 0.87±0.15 4.4 0.0011 16.2±15.3 3.9 Eu 778.9 0.99±0.14 6.5 0.0051 6.3±15.4 0.5 Eu 964.1 0.75±0.40 5.2 0.0038 24.6±15.8 1.8 Eu 1085.9 0.96±0.25 4.9 0.0062 1.4±14.55 2.1 Eu 1112.1 0.98±0.15 10.2 0.0076 6.6±15.2 0.01 Co 1173.2 0.98±0.26 15.3 0.0037 3.5±15.8 4.60E-05 Co 1332.5 1.04±0.18 10.9 0.0030

• 23.9±15.9

0.01 Eu 1408 1.04±0.18 7.0 0.0044 3.1±16.2 0.7

Annual Oscillations in a Few Peaks, but Low Significance

USP 73 – Palmer Station, Antarctica

Detail of 60Co 1173keV Peak

• Small Annual Periodicity
• Periodicity gets stronger

in second half of data

• No other spectral features

Annual Peak Nomalized Photopeak Data Frequency (yr-1) Power

Power

USP 73 – Palmer Station, Antarctica

152Eu Branching Ratio

75% Probability

• f Random Occurrence

Detectors do not show Annual Oscillations in 152Eu Branching Ratio Power Frequency (yr-1) Count Power

Power

Frequency (yr-1)

Combined Results - Frequency

0.2 0.4 0.6 0.8 1 1.2 1.4 1.6 1.8 2 200 400 600 800 1000 1200 1400 1600

Frequency [year-1] Energy [keV]

USP71-SandPoint USP73-Palmer USP74-Ashland USP76-Eielson

Annual Oscillations (+ Others) Found in All Detectors Studied

Combined Results - Phase

• 100
• 50

50 100 150 200 250 200 400 600 800 1000 1200 1400 1600

Phase, φ φ φ φ [deg] Energy [keV]

USP71-SandPoint USP73-Palmer USP74-Ashland USP76-Eielson

Phase of Annual Oscillations Reveals a Seasonal Effect

y = 0.0068x + 1.8035 R² = 0.1884 5 10 15 20 25 30 35 40 200 400 600 800 1000 1200 1400 1600

Spectral Power Energy [keV]

Power Linear (Power)

Combined Results – Power

Strength of Oscillations are Greater at Higher Energies

State of Health Data

Data Freq (yr-1) Outdoor Temperature 1.00 ± 0.10 Room Humidity 1.01 ± 0.12 Room Temperature 0.97 ± 0.09 Crystal Temperature 0.96 ± 0.12 Centroid Location (137Cs 661keV) 0.96 ± 0.14

152EU Total Br Ratio

none

• Many RASA Diagnostics Show Oscillations
• Changes in Centroid Location Indicate Gain Shift

USP71 Crystal Temperature

Variations in Crystal Temp (±2°) May Explain Periodicities

Conclusions (1/2)

• Several statistically significant frequencies observed

in RASA check source photopeaks

– Annual (~1 yr-1), Rieger (~2 yr-1), Synodic (~10-15 yr-1) – Consistent w/ previous Nuclear Anomaly experiments

• Photopeaks do not always show consistent signals

– Low counts rates impede statistics

• Phase results not consistent with previous Nuclear

Anomaly experiments

– Antarctica φavg < Alaska φavg

Oscillations in RASA Check Source Data are Confirmed

Conclusions (2/2)

• 152Eu β-/E.C. Branching Ratio is Constant

– Does Not Support Claims of New Physics Phenomena

• Annual Periodicities Correlate with Crystal

Temperature and other State of Health data

– High frequency content (~10-15 yr-1) is harder to explain

• RASA State of Health Data

– Unique Time-Series Analysis Provides New Diagnostic Utility – Further Study on Crystal Temperature Variations Worthwhile

Oscillations in RASA data are not “New Physics,” but the method provides unique info about IMS RASA operations!

Thank You!

Jim Mattila, Laura Comes, Robin Orth Steve Huber and the entire General Dynamics Team Peter Sturrok, Ephraim Fischbach, Jere Jenkins, Tom Gruenwald Air Force Office of Scientific Research (FA9559-12-1-0027-DEF)

Disclaimer The views expressed here do not necessarily reflect the views

• f the United States Government, the United States Air Force,
• r the Defense Threat Reduction Agency.