Nuclear Physics B Proceedings Supplement 00 (2014) 1–6
Supplement
Cosmic ray detectors for high schools in France
Nicolas Arnauda,∗, Corinne Beratb, Jos´e Bustoc, Gabriel Chardind, Denis Dumorae, Eric Kajfaszc, Antoine Letessier-Selvonf, Benoit Lotte, Arnaud Marsollierd, Jean-Christophe Pelhateg, Morgan Piezelh,
G´erard Tristramf
aLAL, Univ Paris-Sud, CNRS/IN2P3, Orsay, France
bLPSC, Universit´e Grenoble-Alpes, CNRS/IN2P3, France
cCPPM, Aix-Marseille Universit´e, CNRS/IN2P3, Marseille, France
dCNRS/IN2P3, 3 rue Michel-Ange, 75016 Paris, France
eCENBG, CNRS/IN2P3&Univ. Bordeaux, 33170 Gradignan, France
fLPNHE, UPMC, Universit´e Paris Diderot, CNRS/IN2P3, France
gProfesseur de physique-chimie, lyc´ee Jean-Pierre Vernant, 92310 S`evres, France
hProfesseur de physique-chimie, lyc´ee Camille Claudel et Universi´e de Technologie de Troyes, 10000 Troyes, France
Abstract
In France, the CNRS National Institute for Nuclear Physics and Particle Physics (CNRS/IN2P3) is involved in educational actions promoting the use of cosmic ray detectors in high schools. These projects are ran in close collabo- ration with teachers to ensure that they match the letter and spirit of the curriculum. These instruments, lent to teachers for periods ranging from a few weeks to a few years depending on the measurements possible with them, complement nicely the lectures. They allow the students to sense the elementary particles and to understand the problems raised by their detection. The well-recognized cosmod´etecteur and the new COSMIX detector are described in the following, together with the COSMAX software framework, which gives a direct access to the Fermi satellite data.
Keywords:
Cosmic rays, Detectors, Education, Gamma rays, Outreach
1. Introduction
1
After some years of eclipse, topics related to particle
2
physics – special relativity, the lifetime of the muon, the
3
radioactiveβdecay, etc. – are now back in the French
4
high school physics curriculum. Introducing these sub-
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jects at high-school level is a real challenge. In addi-
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tion to the limited knowledge of students at this level in
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mathematics and physics, there is no easy window onto
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the world of the infinitely small. As radioactive sources
9
are now forbidden in schools, cosmic rays remain the
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only way to show particles to teachers and students and
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to study their interactions with matter.
12
∗Corresponding author
Email address:[email protected](Nicolas Arnaud)
A good detector for an educational experiment based
13
on cosmic rays should be compact and light enough to
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be installed in a classroom, at the same time both effi-
15
cient and robust, and, last but not least, its use should
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be as straightforward as possible. In France, the Na-
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tional Institute for Nuclear Physics and Particle Physics
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of the CNRS (in short CNRS/IN2P3) is using its high
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expertise in particle physics detectors to design, build
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and maintain cosmic ray detectors for high schools. The
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two main such projects, the ”cosmod´etecteur” [1] and
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the ”COSMIX” detector [2], are described in the fol-
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lowing. Devices more suited to outreach exhibits, like
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the ”Cosmophone” or the ”Cosmic Arch”, exist as well.
25
As the number of cosmic ray detectors available to
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teachers is limited, complementary approaches are pur-
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sued in parallel. Following the successful example
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briefly described at the end of these proceedings.
33
Le mystEre des RAYONS COSMIQUES
2012 Les rayons cosmiques ont 100 ans ! Une exposition réalisée par l’IN2P3, l’Institut National de Physique Nucléaire et de Physique des Particules du CNRS, à l’occasion du centenaire de la découverte des rayons cosmiques.
. Françoise AmaAmaAmat (t (t (LUPLUPLUPM MM MM Montontontpelpelieeer)r)r) . Nicolas Arnaud (LALLALAL Orsay) . Corinne Bérat (LPSC Grenoble) . Armand Fiasson (LAPP AAAnnennncy) . Jean-Pierre Lees(L(APPAnnececcy)yy . A A
. Arnarnaudud dMarMsolsolsollielielier (r (CNRCS/IN2PN2P3/C3/C3/ERN) .. GGilles MauMauMaurinrinrin(L(L(LAAPPA Annecy) . Jeanean-Lu-L-Lc Rc Robeobebrt rt(AP(APAPC PCaris) . Catherine Thihibaubaubault lt (CSCSCSNSMNSMNSMOrOrOrsasays) Coo Coo Coordrdrdinationionon : . Françoiçoiose sAmat (t ( (LUPLUPLUPM MM MM Montontonpelpelpellielielir) . Arnaud dMarMarMarsollier (r (CNRNS/I/IIN2PN2PN2P3/C3/C3/CERNEE) C
Con Concepction grapapphiqhique ue:
. Arnaud MarMaMsollier (CNRNRNRSS/ISNP2P3/P3/P3/CERCERCERN)) . C
. . hristopheeeMeMMrcier (LUPMPMPMMontpeeellillillieer)er) Rem
Rerciements pour leur aidde pe pe précrieuse : Ch
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Christina Cantrntrtrelelel(CN(C(CRS/SIN2P3), GabGriel Chardin (CNCNNRS/RS/RS IIIN2P3)P3)3),,,DanDanDanielielielDeDcamp (LAPP Annecy), Fabbricrice Feinnnssstein n (LUUPM Montpellier), Christine Hadrossek (CSNSM SMSM OrsOrsOray), Cla
C
Crisse e HamHadaadaadche (CS(CSNSMCSNSMNSM Orsssay)aa Bernard Pd Pdellequer ((CERN)RN)RN), Brigitte e PerPerPerucuccuca (CNRS)
Images de fond: © US Army signal center,Brookhaven National Laboratory, CERN, Emmanuelle Martinez, Tom Bärfuss. Composition: Arnaud Marsollier
16.indd 1 02/10/12 18:19
Figure 1: Poster of the 2012 CNRS/IN2P3 exhibit, called ”The mys- tery of the Cosmic rays”. The exhibit first shows a timeline of the study of the cosmic rays, from the first observations of electroscope self-discharges to the moment, shortly after World War II, when parti- cle accelerators replaced cosmic ray observatories as primary tools to study the elementary particles. The second part of the exhibit presents a panorama of the current experiments and techniques used to study the energetic particles coming from the cosmos.
Finally, a low-cost and easily transported exhibit [5]
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has been prepared by the CNRS/IN2P3 in 2012 to cele-
35
brate the 100th anniversary of the cosmic ray discovery
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by Viktor Hess – see the exhibit poster in Fig. 1. In-
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terested teachers can either loan a copy of the exhibit
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hosted by one of the participating CNRS/IN2P3 labo-
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ratories, or print the panels on their own to get a per-
40
manent copy. The high-definition files of the 16 panels
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making up the exhibit are available for free on request.
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2. The cosmod´etecteur
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In France, a collaboration started several years ago
44
between the CNRS/IN2P3 and ”Sciences `a l’ ´Ecole” [6],
45
a ministerial plan from the French Education Ministry.
46
Large cosmic ray detectors called cosmod´etecteurs are
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tors and secondary teachers attributes the most appro-
52
priate teaching materials for classroom use.
53
2.1. The cosmic ray detector
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Figure 2: A cosmod´etecteur.
A cosmod´etecteur consists in three mobile plastic
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scintillators, each coupled to a photomultiplier (PMT)
56
on top – see Fig. 2. The scintillators can be arranged
57
in different geometries in order to perform several com-
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plementary experiments (flux and angular distribution
59
of the cosmic rays, Auger-like [7] and Rossi [8] shower
60
experiments, etc.). The data acquisition (DAQ) system
61
is able to trigger on twofold or threefold time coinci-
62
dences between scintillator plates, which efficiently re-
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moves the background. A Labview interface is used to
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steer the detector, to monitor the data taking and record
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data in ASCII format. Two additional elements are in-
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cluded with the cosmod´etecteur – see Fig. 3.
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• A Cherenkov radiator coupled to a PMT via a light
68
guide, which is used to prove that cosmic muons
69
come from above: students can note that depend-
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ing on the inclination of the detector, the PMT de-
71
tects photons or not. An explanation of this exper-
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imental fact can be found knowing that Cherenkov
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photons are emitted in a cone along the path of a
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cosmic muon whose speed exceeds the speed of
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light in the radiator.
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• A thick plastic scintillator tube (2.3 liters) which is
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used to measure the muon lifetime: when a muon
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enters in the scintillator and stops, it triggers a first
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signal; later, it decays into an electron or a positron
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No counting
Counting PMT
Measured lifetime = 2.26 s
Cherenkov radiator Thick in a light guide scintillator
Figure 3: Two more experiences possible with the cosmod´etecteur. Left: a demonstration that cosmic muons come from above; right: a measure- ment of the muon lifetime.
(and a neutrino-antineutrino pair) which triggers
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the second signal. As the timing resolution is at
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the level of a few tens of ns, the histogram of the
83
difference between the two timing signals can be fit
84
by an exponential distribution whose parameter is
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compatible with the muon lifetime – about 2.2µs.
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The full price of a cosmod´etecteur is about 8,000e,
87
including a laptop and a transportation box.
88
2.2. Partnership with Sciences `a l’ ´Ecole
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Sciences `a l’ ´Ecole (”Science at School”) is a French
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ministerial plan created jointly by the National Educa-
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tion Ministry and the Higher Education and Research
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Ministry in March 2004, which purpose is to renew the
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teaching of sciences in the French school system, from
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secondary schools to classes preparing for entrance to
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the French ”Grandes Ecoles”. It therefore contributes to
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the development of scientific vocations among young-
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sters, as well as promotes sciences as a way for the
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most part to achieve successful studies. Its action is
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based on three main pillars. First, it provides a finan-
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cial support to projects bringing scientists to classes or
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creating educational resources. Then, scientific equip-
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ments are lent to high schools. The ”Cosmos `a l’ ´Ecole”
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(”Cosmos at School”) program [9] is in charge of the
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cosmod´etecteurs while similar programs exist for other
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fields: astronomy, seismology, genetics, meteorology,
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etc. Each program, called also equipment plan, is based
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upon a partnership between ”Sciences `a l’ ´Ecole” and the
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different research institutes of the particular field. Fi-
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nally, the plan encourages teams of students to take part
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in science challenges at the national level and drives the
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French representation to international ones.
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2.3. Educational activities based on the cos-
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mod´etecteur
114
The teachers selected by Cosmos `a l’ ´Ecole are trained
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prior to receiving the cosmod´etecteur. They follow a
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one week-long seminar at CERN – the French part of
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the High School Teacher program [10], sponsored by
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the CNRS/IN2P3 and Sciences `a l’ ´Ecole and which
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involves about 35 participants each year – plus a 3-
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day technical course in CPPM to learn how to use the
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apparatus. Each teacher which has been lent a cos-
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mod´etecteur benefits from an educational leaflet which
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includes an introduction to particle physics, a descrip-
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tion of the detector, various information about its op-
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eration and the data analysis methods, such as a list of
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suggested measurements to carry out. They can also
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get advices from a CNRS/IN2P3 physicist who acts as a
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mentor (and not as an operator for the cosmod´etecteur),
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plus some support from the teacher academic author-
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ity. Meetings are regularly organized to get the teach-
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ers’ feedback and to allow them to present to colleagues
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the educational activities they have developed based on
133
the detector.
134
The cosmod´etecteur network is shown in Fig. 4: it
135
counts 46 high schools (representing more than 1,100
136
students) from 18 out of the 26 education academies.
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Figure 4: High schools equiped with a cosmod´etecteur.
There are currently 17 such detectors in France and 15
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more will be released in 2014 thanks to the French ”Pro-
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gramme d’Investissements d’Avenir” that enables the
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funding. These devices are operated over long periods
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in order to fully exploit their potential. Therefore, they
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remain several months in the same location, under the
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responsibility of reference teachers educating their col-
144
leagues about using them. By default, a team of teachers
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gets a cosmod´etecteur for three years and usually makes
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it available, first in their high school and then locally.
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The cosmod´etecteur is routinely used by teachers as
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a part of their pedagogical projects. As an example, in
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the framework of the 2010 French Physics Olympiad,
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a project based on a cosmod´etecteur has been awarded.
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With the new scientific high-school curriculum, the de-
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tectors are now used during regular teaching hours and
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not just for research projects or hands-on activities.
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In addition to the physics measurements highlighted
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above, the cosmod´etecteur also brings a true hands-on
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experience to teachers. Prior to using the detector, they
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have to calibrate the PMTs by performing the so-called
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”plateau measurements” (raising in steps the PMT high-
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voltage until the detection efficiency of the correspond-
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ing scintillator plates flattens offat a constant level close
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to 100%). Moreover, they have to understand signal dis-
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crimination and coincidence measurements.
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2.4. Prospects
164
In the medium term, the teacher network will have
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to be strengthened. Two initiatives have already been
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taken to meet this challenge: first, an online forum
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new educational resources related to particle physics.
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This requires new synergies with other existing edu-
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cation/outreach projects like the International Master-
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classes or the ”Passeport pour les deux infinis”. Indeed,
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all these activities are coordinated by the ”Ecole des
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deux infinis” [11] at the CNRS/IN2P3 level.
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3. The COSMIX case
178
Two years ago, the Gradignan CNRS/IN2P3 labora-
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tory (”Centre Etudes Nucl´eaires de Bordeaux Gradig-
180
nan”, in short CENBG) started developing a different
181
cosmic ray detector, called COSMIX. Its main innova-
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tion is to be highly portable as it fits in a small case
183
and is plug-and-play. It allows a quick and easy intro-
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duction to cosmic rays to audiences which do not have
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access yet to a cosmod´etecteur.
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3.1. The detector
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Display CsI(Tl) bar CsI(Tl) bar
Electronics DAQ
•Display
•Storage
•GPS
•Altimeter
Control
Figure 5: COSMIX case prototype.
Figure 5 shows the contents of a COSMIX case. The
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detector uses two scintillator bars made by cutting in
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two a spare CsI(Tl) bar from the Fermi-LAT satellite de-
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tector, connected to Hamamatsu PIN diodes and custom
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electronics – the DAQ system is based on an Arduino
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micro-controller. It includes a GPS, a pressure-meter
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and a DAQ system allowing data to be stored onto a SD
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memory card. It is powered by a simple USB connec-
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tion, provided for instance by a laptop, and drives about
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300 mA. The total weight is below 4 kg. The cost of a
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Single rate Coincidences
[One bar is movable]
~1 evt/s ~0.4 evt/s
Figure 6: The two measurements possible with the COSMIX case: single or coincidence rates.
COSMIX case is about 1,000e; a reduction of a factor
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two has been achieved by recycling existing detectors
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and electronics.
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3.2. Measurements
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No setting nor calibration is required to take data with
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a COSMIX case – just to power it. The energy deposited
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in a bar by a cosmic muon is about 12 MeV, a value
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much higher than those due to background. Therefore,
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all analog-triggered signals come from real muons. Two
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data taking modes, illustrated in Fig. 6, are possible: the
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single bar rate is about 1 event/second while the coinci-
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dence rate (one bar is movable and can thus be put on
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top of the other) decreases to about 0.4 event/second.
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Moreover, as all high schools in France have digital
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scopes nowadays, they can use them to trigger on the
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PIN diode outputs to see the signals associated with sin-
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gle or coincidence detections.
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Figure 7 shows an example of a COSMIX measure-
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ment performed over several hours. The huge rate vari-
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ation corresponds to a commercial flight, while the de-
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crease at time∼24000 s can be traced to a trip in the
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Paris subway. Smaller but clearly visible rate variations
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have also been recorded during private plane flights.
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Many applications are possible for this detector: short
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introduction to cosmic rays in classrooms, demonstra-
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tions at the end of a public lecture or during an exhibit,
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etc. A collaborative website will allow participating
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teachers to publish their data while describing how they
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were acquired. One example: teachers from everywhere
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in France could be able to study the cosmic ray rates at
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Rate (particles/minute)
Time (s)
Figure 7: Example of measurement with the COSMIX case.
the different floors of the Eiffel tower, hence reproduc-
228
ing Theodor Wulf’s experiment from 1909 [12].
229
3.3. Rolling-out the COSMIX detectors
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In 2013, three test cases (among which two were
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funded by Sciences `a l’ ´Ecole) circulated in the Bor-
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deaux area: more than 1,000 students from 15 high
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schools used the COSMIX detector and their feedback
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helped improving its design. One of these prototypes is
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now in the Reunion Island (in the Indian Ocean, east of
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the Madagascar island), a place where there are very ac-
237
tive teachers interested in particle physics, but which is
238
too far from mainland France to get a cosmod´etecteur.
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This example illustrates the complementarity between
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the two types of detectors.
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This year 2014 is the first mass production year for
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the COSMIX case: 10 have been produced for the Paris
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4. COSMAX
248
The COSMAX (”COSMic ACCelerators”) project is
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software-based and developed by the same CENBG
250
team as the COSMIX case. It is based on a suite of
251
tools installed on a ready-to-use linux virtual machine –
252
or directly on linux. It aims at providing access to the
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very variable gamma ray sky using the Fermi-LAT data.
254
These data are public, readily available, easy to grasp
255
(photon detection time, measured energy and recon-
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structed incoming direction on the sky) and all-sky. The
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data analysis tools are the same than those used by the
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scientific community. They allow the users to produce
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time-resolved maps or animations and to study many
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transient phenomena like blazars, gamma ray bursts or
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pulsars. Figure 8 shows one example of the sky maps
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which can be produced in the COSMAX framework.
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Figure 8: Sky map integrating one week of Fermi data produced with the COSMAX framework. At coordinates L=86.1 and B=−38.2 one can see the very variable 3C 454.3 blazar (discovered by the Fermi satellite), at that time the brightest gamma source in the sky.
Now that the package is fully-functional, the next step
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will be to improve the user interface to allow users with
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only a basic knowledge of computing to use this frame-
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work and achieve results. Indeed, our experience has
267
shown that the computing skill of high-school teachers
268
are very variable.
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5. Conclusions
270
The CNRS/IN2P3 and its partners, among which Sci-
271
ences `a l’ ´Ecole, are developing educational projects
272
based on particles coming from the cosmos: both
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a decade ago. It combines the CNRS/IN2P3 physical
278
and technical knowledge with the Sciences `a l’ ´Ecole
279
educational expertise to produce large cosmic detectors
280
lent to selected teachers which then get some support
281
(resources, advices) to operate these complex devices.
282
Thanks to this project, more and more high-school stu-
283
dents and teachers will discover particle physics through
284
cosmic rays. The new IN2P3 COSMIX detector, mo-
285
bile and easy to use, is a different tool which offers
286
new opportunities to provide an introduction to cosmic
287
rays to audiences which do not have access to a cos-
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mod´etecteur. Finally, the COSMAX software project
289
allows to study the gamma rays detected by the Fermi
290
satellite by making use of the fact that these data are
291
simple to understand and easy to manipulate.
292
Acknowledgment
293
The authors would like to thank Sciences `a l’ ´Ecole
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for its support of CNRS/IN2P3 outreach activities, and
295
in particular Mrs. Sol`ene Chevalier-Th´ery and Claire
296
Bonnoit-Chevalier.
297
References
298
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299
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