# Presentation: 524082

## Advanced Thin Ionization Calorimeter

- Jim Adams

## Outline

- Description of the ATIC instrument
- Some of the Scientific Results from the first ATIC flight
- Balloon Launch Failure on the Third ATIC flight

## Measurement Objectives

- H and He Spectra from 1010 to 1014 eV/particle
- Individual elemental spectra from 1010 eV/particle for the elements Li – Fe
- Electron Spectrum from 2X1010 eV

## ATIC Instrument

## Actual Instrument

## Silicon Matrix

-  4 1.5X2 cm2 silicon pads per daughter board
-  28 daughter boards per mother board
-  2 motherboards per ladder
-  10 ladders per panel
-  2 panels with 4480 pads total

## Three Scintillator Hodoscopes

- Bicron BC-408 scintillator strips (1cm X2 cm) read out from both ends with Hamamatsu R5611 PMTs

## BGO Calorimeter

-  2.5cm X 2.5cm X 25cm bismuth germanate crystals
-  20 crystals per half tray, each viewed from one end by a Hamamatsu R5611 PMT
-  40 crystals per tray
-  8 trays

## Science Objectives

- Investigate the nature of the cosmic ray accelerator
- Look for evidence of more than type of source
- Test diffusive shock acceleration models
- Investigate galactic confinement
- Test “leaky box” and “diffusion” models
- Investigate cosmic ray leakage from the Galaxy
- Investigate the role of re-acceleration
- Examine the electron spectrum for evidence of nearby cosmic ray sources

## The Energy Spectrum

- ATIC
- energy
- range

## Sources and Acceleration

- Sources: Probably Type II Supernovae
-  CR energy density  1eV/cm3
-  Residence time in the galaxy  2.6x107 yrs
- Power required ~2.5X1047 ergs/yr
- A Type II Supernova yields ~1053ergs
- Almost all of it goes into neutrinos
- 1051 ergs in the blast wave
- SN rate  2/century  2X1049ergs/yr
- Blast wave must convert ~1% of its energy into cosmic rays.
- Diffusive Shock Acceleration required

## Diffusive Shock Acceleration

- Jokipii Model

- Cesarsky Model

## New HESS TeV -ray Observations

- RX J852.0 - 4622

- RX J1713 - 394

-  These TeV -rays are clearly from the SNR blast waves but are they from P+PP+P+0 P+P+2?
- - The -rays could be from electrons, but this requires higher magnetic fields than are thought to exist in SNRs

## Are All Supernova Cosmic Ray Sources of the Same Type? 

- Are All Supernova Cosmic Ray Sources of the Same Type?

- No. If all sources were the same type, all the elemental spectra above 102 Gev/nuc would have the same shape and they don’t. There must be at least two types. Biermann has suggested that the two types are 8-15 Mʘ stars and Wolf-Rayet stars.

## Our Galaxy

- Diameter = 30 kpc
- 	(1 parsec = 3.26 light years)
-  Disk thickness = 300 pc
-  Sun: 2/3 out from the center and a little north of the middle
-  Interstellar medium: gas, dust & cosmic rays
- - Density ~ 1atom/cm3
- Energy densities in gas, cosmic rays and magnetic field are all ~1 eV/cm3
- Magnetic field ~ 5 G
- At 1.5X1017eV the Larmor radius of a proton is 30 pc

## Cosmic Ray Confinement Models

**Leaky Box Model**
-  Cosmic rays confined to a box with leakage at the boundary.
-  Within the box, cosmic only interact with interstellar gas

**Halo Diffusion Model**
-  Cosmic rays diffuse through magnetic scattering centers in the Galaxy
-  The densities of scattering centers and gas are highest in the Galactic disk but extend into a halo above and  below the disk
-  Cosmic rays interact with the gas in the Galaxy and escape by diffusion

## Cosmic Ray Confinement

- Re-acceleration due to scattering during diffusion has been added (see Heinbach and Simon, Ap. J. **441**, 209** **(1995)

## ATIC-2 Results

- The ATIC H and He spectra are fit by a diffusion model that includes weak re-acceleration due to Kolmogorov turbulence (Osborne and Ptuskin, 1988) but different source spectra for H and He are required.

## Balloon Launch Facts

- Balloon volume 30,000,000 cu. ft.
- Balloon length ~200 ft
- Helium bubble at launch ~100,000 cu. ft.
- Gross Lift ~6,700 lbs
- Balloon mass  Payload mass  3000 lbs
- Free lift ~670 lbs
- Ascent rate ~1000 ft/min

## Slide 20

## Launch Considerations

- Surface winds < 15 knots (lower is better)
- Winds should be steady in speed and direction for >2 hours
- _The vertical wind gradient from the ground to ~300 ft altitude should be small_
- Winds aloft should be circumpolar

## Notice: 1) how the bubble is distorted by the wind and 2) the absence of a sounding balloon

##  Notice the shape of the balloon

-  Notice the shape of the balloon
-  The balloon  is not ascending vertically. A strong wind shear has distorted the balloon
-  The reefing sleeve has already split all the way to the parachute.

## Landing