Cosmic ray science with EUSO-SPB1personalpages.to.infn.it/.../Alisson_OralExam.pdf · 2018. 8. 10. · 1 EC = 2x2 Multi-Anode Photo-Multipliers Tubes (MAPMTs) 1 MAPMT = 8x8 pixels

Cosmic ray science with EUSO-SPB1

December, 21st Alisson Michel 1

Supervised by: Prof. Mario Bertaina

Outline• Cosmic rays & Atmosphere

✤ Extensive Air Showers ✤ Fluorescence light✤ Cherenkov light

• The Extreme Universe Space Observatory

• The EUSO’s Super Pressure Balloon • Tools & Theory

✤ ESAF✤ Trigger✤ Aperture

• Simulations & Results ✤ EAS study✤ Aperture study✤ SPB1 aperture

• Cloud condition • Conclusions2

Cosmic Rays & Atmosphere

๏ Extensive Air Showers๏ Fluorescence light๏ Cherenkov light

3

Extensive Air Showers (EAS)

nucleus ( N )

atmospherep

p

⇡+

K

⇡�

⇡0

p⌫µ

µ+ ⌫µµ�

e�e+

�

�

⇡0

K

⇡+

⌫µ

µ+

⇡�

e�e+

⌫µµ��

�

• Primary Cosmic Ray (CR) : high energy particle produced in an astrophysical environment

• Collision with atmosphere nuclei

• Cascade of secondary particles

• In each collision : ✤ Kinetic energy is converted into mass

energy + kinetic energy

• Chain reaction is finite : ✤ Creation process is stopped✤ Shower maximun

4

Xmax

Fluorescence

• Fluorescence light production: ✤ Particles ( mostly ) moving through the atmosphere

excite metastable energy levels in molecules✤ Ionizing excitation of mostly Nitrogen molecules✤ Spontaneous de-excitation ✤ Isotropic emission of fluorescence light along the

EAS

5

NN

NN

NN

excited molecule

Energy deposited

De-excitation : UV emission

~ 330 - 400 nm

#. flu

o. p

hoto

ns

Atmosphere depth

Xmax

e�

Cherenkov

• Numerous secondaries have velocities higher than the speed of light ( )

• Cherenkov emission : ✤ Photons are beamed in a cone

(~1,3°) along the trajectory✤ Scattering by the molecular and

aerosol content of the atmosphere

✤ Reflexion when particles reach land, sea or clouds

6

v >c

n

7

Fluorescence

Air scattering Cherenkov

Reflected Cherenkov

p atmosphere

Light development in an EAS

Clouds, Land, Oceans

#. of

phot

ons

The Extreme Universe Space Observatory

8

• 16 Countries, 91 Institutions, more than 300 researchers

• EUSO’s aim : JEM-EUSO Space telescope on the ISS Japanese Experiment Module

• Image the Nitrogen UV Fluorescence and Cherenkov track from above

• Aim to efficiently detect the highest CRs

• JEM-EUSO and its pathfinders: ✤ EUSO-TA (2013-), EUSO-Balloon (2014), TUS (2014),

EUSO-SPB1 (2017)✤ Mini-EUSO (2018), SPB2 (2021), K-EUSO (2023),

POEMMA (2025)

The Extreme Universe Space Observatory (EUSO)

JEM-EUSO

EUSO-SPB1

9

Ultra-High Energy Cosmic Rays (UHECRs)

• UHECRS :

• Extreme low flux

• Need for great exposure instruments

Flux(m

�2sr

�1GeV

�1)

Energy (eV)Sun

1 particle / m² / second

Knee 1 particle / m² / year

Ankle 1 particle / km² / year

Galactic Extra Galactic

UHEC

Rs

SPB1

1 particle / km² / millenium1 particle / km² / century

E > 1018eV

Exposure x Flux = Number of expected particles

10

The EUSO-SPB1

11

The EUSO on a Super Pressure Balloon (SPB1)

• The EUSO-SPB1 ✤ 8 countries, 50 researchers

• Objectives ✤ Establish techniques and methods for large scale

UHECRs space observatory (JEM-EUSO)✤ Measure the terrestrial UV background light✤ Make the first observation of UHECRs✤ Launch : April, 24th 2017 at 23:51 UTC

• The super pressure balloon : ✤ able to fly at 33km high up to 100 days✤ 1 football stadium carrying 2 cars ✤ Field of view ~11°

• UV camera looking down at night12

• The Photo-Detection Module (PDM) ✤ 3x3 Elementary Cells (ECs)✤ 1 EC = 2x2 Multi-Anode Photo-Multipliers Tubes (MAPMTs)✤ 1 MAPMT = 8x8 pixels✤ 2 304 pixels ( JEM-EUSO : 137 PDMs = 315 648 pixels )✤ Time integration : 2,5 s = 1 Gate Time Unit (GTU)✤ Observational area : 40 km²

1 UHECR particle / 10 days

µ

13

x x

The EUSO on a Super Pressure Balloon (SPB1)

PDM

MAPMT

NZ

Tools & Theory๏ ESAF๏ Trigger๏ Aperture

14

•

• Simu executable : Simulation of the entire physical process (from shower to telemetry )

• Air shower

• Atmosphere

• Optics

• PMT, Electronics

• Trigger

EUSO Simulation and Analysis Framework

15

ESAF

Trigger

• Trigger logic needed to save only significant EAS events

• Exploit peculiarities of the signal morphology with respect to the background

• Look for high concentration of photo-electron counts ‣ in a limited region of the focal surface ‣ within a certain time window

• MAPMT Threshold based on the average pixel count

• Massive screening to recognize an EAS signal

16

Simulated EASin ESAF

Light track produced by an EAS on the detector EAS light track

(integrated over time)

Aperture

• Trigger efficiency - Probability to trigger an event :

• Geometrical aperture :

• Exposure :

Working status of the PDM Clouds Steady or transient lights sources

17

Solid angle were events are injected

Simulated region on ground

✏ =Ntrig

Nsim

A = ✏⇥ k ⇥ ⌦0 ⇥ Ssim

E =

Zdt A⇥ �i

due to simulation selection

Simulations & Results

๏ EAS study๏ Aperture study๏ SPB1 aperture

18



19

• Parameters : ✤ Cosmic Ray energy ( )✤ EAS zenith angle ( )✤ , of the EAS « impact »✤ Balloon Altitude ( )✤ Clouds ( optical depth and altitude )

Simulations in ESAF

33km 17km

Altitude

TimeSPB1 Flight

12 days

E

✓✓

x, y

x y

20

x

E

H

H

EAS Study

Fluorescence Cherenkov

Num

ber o

f pho

tons

• Energy ✤ More the CR is energetic✤ More photons are produced in the shower

• Zenith angle ( ) ✤ More inclined is the shower, brighter is the signal

• Altitude of the detector ( ) ✤ Higher is the detector, Less photons are collected✤ But wider is the field of view

• Clouds : Optical depth (OD), altitude ( ) ✤ Clouds induce greater Cherenkov emission✤ Thicker are the clouds, brighter is the Cherenkov light✤ Higher are the clouds, fainter is the light detected

H

✓

h

21

GTU (Time)

EAS Study


Num

ber o

f pho

tons





H

✓

h

22

GTU (Time)

EAS Study


Num

ber o

f pho

tons





H

✓

h

23

GTU (Time)

EAS Study


Num

ber o

f pho

tons




• Clouds : Optical Depth (OD), altitude ( ) ✤ Clouds induce greater Cherenkov emission✤ Thicker are the clouds, brighter is the Cherenkov light✤ Higher are the clouds, fainter is the light detected

H

✓

h

24

GTU (Time)

EAS Study


Num

ber o

f pho

tons




• Clouds : Optical Depth (OD), altitude ( ) ✤ Clouds induce greater Cherenkov reflexion✤ Thicker are the clouds, brighter is the Cherenkov light✤ Higher are the clouds, fainter is the light detected

H

✓

h

25

GTU (Time)



26

Aperture Study - Energy

• Energy ✤ Efficiency maximum : ✤ Energy threshold :

• Number of events ✤ Better accuracy

27

100 simulated events

1000 simulated events Better accuracy

Ethr

✏max ✏

max

✏max

Ethr

Ethr

�✏ =

r✏⇥ (1� ✏)

N

A = ✏⇥ k ⇥ ⌦0 ⇥ Ssim( )constant

• Altitude of the balloon ( )

Aperture Study - Altitude

• Linear evolution with the altitude: ✤ Energy threshold ( )✤ Efficiency maximum ( )

28

H

Ethr

✏max

Aperture Study - Primary particle

• CR particle : Proton or Iron ? ✤ No difference

29

Aperture Study - Number of working ECs

• Number of working Elementary Cells (ECs) ✤ 9 ECs - 2 possible configurations : ON/OFF✤ Total number of PDM configurations :

- Compute efficiency for each configuration- Efficiency average for each set of same number of « OFF » ECs

• Efficiency proportional to the number of working EC :X [pixel]

0 5 10 15 20 25 30 35 40 45

Y [p

ixel

]

0

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0

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GTU: 7798, pkt: 60, GTU in pkt: 118,

UTC time: 2017-04-28 10:01:56.731385

allpackets-SPBEUSO-ACQUISITION-20170428-100131-001.001--LONG.root

X [pixel]0 5 10 15 20 25 30 35 40 45

Y [p

ixel

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GTU: 4241, pkt: 33, GTU in pkt: 17,

UTC time: 2017-04-26 13:01:33.315495


X [pixel]0 5 10 15 20 25 30 35 40 45

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ixel

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UTC time: 2017-05-01 07:33:09.4053299

allpackets-SPBEUSO-ACQUISITION-20170501-073233-001.001--CHECK.root

X [pixel]0 5 10 15 20 25 30 35 40 45

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UTC time: 2017-04-25 12:28:01.423265


29 = 512

30

Number of “o↵” cells Number of “o↵” cells

1 EC

h✏i✏

Aperture Study - Non uniform PDM efficiency

• Different pixel efficiency in the PDM :

• Effect of the real SPB1 PDM: ✤ The maximal aperture is reduced : 84% ✤ The energy threshold is 1,45 times greater

31

Ethr

Amax

Aperture Study - Background level

• Background level : average number of counts on PDM pixels

• During the SPB1 flight : ✤ Average : 0,85 counts / s / pixel

• and background level :

32

µ

Amax

Ethr /



33

• Simulated in flight conditions at 12 UTC for the 8 first days

• Altitude of the balloon + average background level vgbhkjnkkjn+ Non-uniform efficiency of the SPB1 PDM

Estimation of the EUSO-SPB1 aperture

34


35


• Altitude of the balloon + average background level + Non-uniform efficiency of the SPB1 PDM efficiency



X [pixel]

0 5 10 15 20 25 30 35 40 45

Y [p

ixel

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GTU: 7798, pkt: 60, GTU in pkt: 118, UTC time: 2017-04-28 10:01:56.731385

allpackets-SPBEUSO-ACQUISITION-20170428-100131-001.001--LONG.rootX [pixel]

0 5 10 15 20 25 30 35 40 45

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ixel

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GTU: 4241, pkt: 33, GTU in pkt: 17, UTC time: 2017-04-26 13:01:33.315495


X [pixel]0 5 10 15 20 25 30 35 40 45

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ixel

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20GTU: 127, pkt: 0, GTU in pkt: 127,

UTC time: 2017-04-25 12:28:01.423265

allpackets-SPBEUSO-ACQUISITION-20170425-122750-001.001--LONG.rootX [pixel]0 5 10 15 20 25 30 35 40 45

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20GTU: 660, pkt: 5, GTU in pkt: 20,

UTC time: 2017-05-01 07:33:09.4053299

allpackets-SPBEUSO-ACQUISITION-20170501-073233-001.001--CHECK.root

• Average of the working PDM status on the whole flight


36

Considered as not working

Probability <> Appearance frequency



• Average of the total PDM status on the whole flight


37

64%63,57%

6,93%



• Average of the daily PDM status (finer)

62% 44% 100% 94%

99% 72% 9% 86%


38

Clouds

39

Cloud MODIS satellite

• Database : NASA Earth Data Search

• Terra NASA’s Satellite (700km) ✤ MODIS payload

• Date, 12 UTC , Location of SPB1

• Cloud fraction : 1 : Total cloud coverage0 : No clouds

40

SPB1 cloud coverage

41

• Cloud fraction average on a 1° area : Cloudy !

• Significant parameters unknown : • Cloud top altitude or optical depth

SPB1 cloud coverage

52%61%

80%91%

90%100%

76% 73% 100%97%

87% 78%

±

42

April, 25thApril, 30th

May, 3rd

May, 6th

May, 1st

April, 27th

✤ There is still hope

Conclusions

43

Conclusions

• Aperture of EUSO-SPB1 ✤ Studied and quantified the

aperture dependency on :- The energy of the primary cosmic ray- The altitude of the balloon and background

level- The status and real efficiency of the PDM

✤ Estimated of the aperture for each day at 12 UTC

• What can be done : ✤ More precise estimation of the

aperture by finer parameters✤ Repeat for times in the flight to get

the expected number of events ✤ Look for more significant data on

clouds44

Grazie mille a tutti per questa bella esperienza

45

Documents

Cosmic ray science with EUSO-SPB1personalpages.to.infn.it/.../Alisson_OralExam.pdf · 2018. 8. 10. · 1 EC = 2x2 Multi-Anode Photo-Multipliers Tubes (MAPMTs) 1 MAPMT = 8x8 pixels