X-Authentication-Warning: delorie.com: mail set sender to geda-user-bounces using -f X-Recipient: geda-user AT delorie DOT com From: geda AT psjt DOT org (Stephan =?utf-8?Q?B=C3=B6ttcher?=) To: Subject: Re: [geda-user] Raspberry Pi "hat" balloon into the stratosphere next week References: <54282517-6681-7931-7f10-23a9c4882f99 AT neurotica DOT com> Date: Tue, 04 Jul 2017 22:53:12 +0200 In-Reply-To: (John Griessen's message of "Tue, 4 Jul 2017 11:54:07 -0500") Message-ID: User-Agent: Gnus/5.13 (Gnus v5.13) Emacs/24.5 (gnu/linux) MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: 8bit X-MIME-Autoconverted: from quoted-printable to 8bit by delorie.com id v64KrGBP018827 Reply-To: geda-user AT delorie DOT com Errors-To: nobody AT delorie DOT com X-Mailing-List: geda-user AT delorie DOT com X-Unsubscribes-To: listserv AT delorie DOT com Precedence: bulk "John Griessen (john AT ecosensory DOT com) [via geda-user AT delorie DOT com]" writes: > On 07/03/2017 02:57 PM, Stephan Böttcher wrote: >> No, sorry. What I have is for the RPi1. I hope to launch it on a >> balloon into the stratosphere next week: >> >> http://www.ieap.uni-kiel.de/et/people/stephan/rpirena/ > > "The scatterplot shows the pulse height of channel 2 vs channel 3, the > histograms show cosmic muon spectra in those channels." > > So is the histogram chart x axis nanometers wavelength? No, these are approximate mV pulse height of the shaper outputs. I did not calibrate the energy scale. The pulse height is proportional to the energy deposited in the silicon detectors by ionization. The red dots are hits by muons, which are generated as secondary particles from cosmic radiation in about 20km height above ground. Muons have a half-live of a few microseconds, but travel close to the speed of light, so in their reference frame the distance to ground is compressed to a few meters. Muons pass through matter without cascading into secondary particles, they just loose energy by ionization like any particle with charge 1 at the speed of light (Minimum Ionizing Particles, MIPs). That is how they reach ground. All other particles cascade into showers of particles until the energy is distributed so much that they get stopped, well above ground. Muons eventually decay into an electrons and two neutrinos. In these silicon detectors with thickness 300µm, muons loose on average 115 keV at vertical incidence. That energy is converted into electron hole pairs inside the fully depleted silicon diode, 1 pair requires 3.6eV. The muons produce about 30000 electrons. The electronics amplifies this charge pulse to a voltage pulse, which is sampled at 3MSPS and analysed by a digital filter. The muon hits are identified by the fact that both detectors are hit at the same time. Most of the other hits are also muons which miss the other detector. Other hits may be due to x-rays or Compton scattering from gamma rays from the environment. The peaks in the spectra show the distribution of the energy deposits of the muons. This is called the Landau distribution, here folded with the path-length distribution due to angle of incidence, and background. If you project just the red dots to either axis, a cleaner Landau distribution results, with less background and less path length variations. > If so, what does the spike at 0 with zero notch at 10 or 20 mean? The spike at zero is the electronic noise measured when the other detector was hit. The notch is the gap between the noise and the trigger threshold. The pulse heights are sampled from the digital filter outputs when either channel has a peak of more than 15mV. > Is some of the energy really at effective "wavelengths" below 10 nm? > > If the scale is in nanometers, the slope up towards 10nm is more and > more UV light. Would that be coming from ionized air inside the dark > box? Ionized traces of outgassing circuit materials? That slope can be the tail of the noise or indeed some x-ray background. It looks like the tail of the noise to me. > Is the gamma ray energy all in the high high frequency spike at or > near zero? Gamma rays are difficult to measure in silicon detectors. You need a heavy detector with high-Z atoms inside to completely convert a gammy photon into ionizing energy loss. The big box in that photo contained at that time a CsI salt crystal, which can absorb gammay rays, and converts the ionization enrgy into flashes of light. This is called a scintillator. The light can be measured with the same kind of silicon photodiodes. The calibration is not as easy, since the light yield depends on temperature and doping of the scintillator, on the shaping time of the electronicsm and the resulting balistic deficit, which is the light that comes to late to be integrated by the shapers. The time profile of the light emission depends on temperature as well. In silicon, the gamma rays can be seen by Compton scattering. The gamma kicks an electron, which then deposits part of the gammas energy in the detector. The amount of energy depends on the elastic scattering angle of the photon, up to a maximum when the photon is scattered 180°. That maximum can sometimes be measured, when monoenergeic gamma rays from a radioactive source are used. This is more difficult if the Comptom electrons can escape the detector with some of the energy unseen. Too much information? Gruß, -- Stephan