The Colorado Inner Radiation Belt Experiment, or CIRBE, was launched on April 15th, 2023, into a sun-synchronous orbit with a 97.4o degree inclination and a 509 kilometer altitude. CIRBE is partitioned into two sections: a spacecraft bus (XB1 from Blue Canyon Technologies), and its only science payload, Relativistic Electron Proton Telescope integrated little experiment-2, or REPTile-2.
REPTile-2 is a 10x10x15 cm energetic particle telescope. It includes four 1.5 mm thick silicon detectors (‘D1’ through ‘D4’) separated into inner areas (diameter 20 mm) and outer rings (diameter 40 mm), which are known as guard rings (‘G’). These detectors were obtained from Micron Semiconductors, UK. In front of the silicon detectors there is a beryllium window with a diameter of 20 mm and a thickness of 0.3 mm that block <~200 keV electrons and <~6 MeV protons from reaching the silicon detectors. In front of the beryllium window, a collimator is used to prevent particles from outside the telescope’s field of view of ~51o from entering the detector stack.
REPTile-2 has a high energy resolution and is capable of measuring electrons from ~0.25-6 MeV and protons from ~6.5-100 MeV via the 120 total energy channels used to measure these particles at different energies. Protons and electrons are each dedicated 60 channels, with 50 of those measuring range particles and 10 of them measuring penetrating particles. It also has an extremely high time resolution capable of distinguishing events occurring merely 400 nanoseconds after each other.
For more information about REPTile-2: here
Logic Information
REPTile-2 records an event when a particle enters the detector stack and deposits energy on one or more detectors. The instrument uses a system of logic to determine which events are considered valid and to categorize valid events into one of four categories corresponding to what kind of particle is being measured: range protons (RNGp), penetrating protons (PENp), range electrons (RNGe), and penetrating electrons (PENe).
Valid events are events that deposit an amount of energy that is above a certain threshold (TD) on the first detector (D1) and do not deposit an amount of energy that is above another threshold (TG) on the guard rings (G). TD and TG are set at 100 keV and 671 keV, respectively. This means that if an event deposits more than 100 keV on D1 and less than 671 keV on G, it is considered to be a valid event.
Events are further classified via the use of two slant equations. The first slant equation, D12s, is true if the energy deposited on D1 divided by 2.8 MeV plus the energy deposited on D2 divided by 4.2 MeV is greater than 1. If D12s is not true then the event is an electron. The event is further classified as either a range or a penetrating electron by whether or not TD is deposited on D4; if TD is deposited on D4, the event is a penetrating electron (PENe), and if not, the event is a range electron (RNGe).
The second slant equation, D34s, is true if the amount of energy deposited on D3 divided by 13.5 MeV plus the amount of energy deposited on D4 divided by 30 MeV is greater than 1. If both D12s and D34s are true and TD has not been deposited on D4, the event is classified as a range proton (RNGp). If only D12s is true and TD has been deposited on D4, the event is classified as a penetrating proton (PENe).
The logic equations are summarized in the table below taken from: Khoo, L.-Y., Li, X., Selesnick, R. S., Schiller, Q., Zhang, K., Zhao, H., et al. (2022). On the challenges of measuring energetic particles in the inner belt: A Geant4 simulation of an energetic particle detector instrument, REPTile-2. Journal of Geophysical Research: Space Physics, 127, e2021JA030249. https://doi.org/10.1029/2021JA030249.
Energy Channel Information
Each of the four categories is dedicated a range of energy channels, with each channel corresponding to a certain particle energy. The particle type, channel energies, and geometric factor times energy channel width (GdE) for each channel as calculated by the bowtie method are shown in the table below.
Channel Number | Particle Type | Energy (MeV) | GdE (cm2sr MeV) |
1 | RNGp | 6.8 | 0.0392272444479054 |
2 | RNGp | 6.8 | 0.0410347259093529 |
3 | RNGp | 6.9 | 0.0413182507919513 |
4 | RNGp | 7 | 0.043823614357862 |
5 | RNGp | 7.1 | 0.0506866384362174 |
6 | RNGp | 7.2 | 0.0518894733226866 |
7 | RNGp | 7.3 | 0.0569562796589815 |
8 | RNGp | 7.5 | 0.0720184011053454 |
9 | RNGp | 7.6 | 0.0698009920443771 |
10 | RNGp | 7.7 | 0.0754675359633083 |
11 | RNGp | 7.9 | 0.0776797680914494 |
12 | RNGp | 8.1 | 0.0838597832119609 |
13 | RNGp | 8.2 | 0.0862950938748381 |
14 | RNGp | 8.4 | 0.10190163290902 |
15 | RNGp | 8.6 | 0.0998505287432661 |
16 | RNGp | 8.9 | 0.121482935529745 |
17 | RNGp | 9.1 | 0.125365793689071 |
18 | RNGp | 9.4 | 0.136192429199833 |
19 | RNGp | 9.6 | 0.138826261654679 |
20 | RNGp | 9.9 | 0.149855188681277 |
21 | RNGp | 10.2 | 0.161971246127969 |
22 | RNGp | 10.6 | 0.178305325456198 |
23 | RNGp | 10.9 | 0.180748486870869 |
24 | RNGp | 11.3 | 0.188379176521905 |
25 | RNGp | 11.7 | 0.20600782158654 |
26 | RNGp | 12.1 | 0.218832723432197 |
27 | RNGp | 12.6 | 0.234544446932618 |
28 | RNGp | 13.1 | 0.26588330108469 |
29 | RNGp | 13.6 | 0.254699883086223 |
30 | RNGp | 14.1 | 0.267324019322415 |
31 | RNGp | 14.7 | 0.290400499253022 |
32 | RNGp | 15.3 | 0.30497435535352 |
33 | RNGp | 16 | 0.350671678121021 |
34 | RNGp | 16.7 | 0.341609611569272 |
35 | RNGp | 17.4 | 0.335591504245762 |
36 | RNGp | 18.2 | 0.355100677038051 |
37 | RNGp | 19 | 0.355539287991945 |
38 | RNGp | 19.8 | 0.375758786843855 |
39 | RNGp | 20.8 | 0.414962626539929 |
40 | RNGp | 21.7 | 0.412125823391869 |
41 | RNGp | 22.7 | 0.427594167581035 |
42 | RNGp | 23.8 | 0.451653146373649 |
43 | RNGp | 24.9 | 0.433352598042547 |
44 | RNGp | 26.1 | 0.441347501542973 |
45 | RNGp | 27.4 | 0.49000872334778 |
46 | RNGp | 28.7 | 0.505489489225791 |
47 | RNGp | 30.1 | 0.466614938381014 |
48 | RNGp | 31.6 | 0.4057175118402 |
49 | RNGp | 33.1 | 0.527043656420538 |
50 | RNGp | 34.5 | 0.179635941840052 |
51 | PENp | 95.1 | 3.6262936568183 |
52 | PENp | 32.3 | 0.318290237272177 |
53 | PENp | 34.6 | 0.382979559546845 |
54 | PENp | 37.2 | 0.719428002135456 |
55 | PENp | 39.4 | 1.17338020904926 |
56 | PENp | 48.8 | 4.09986951288032 |
57 | PENp | 54.7 | 6.79403446819182 |
58 | PENp | 63.4 | 11.9634539965272 |
59 | PENp | 76.9 | 21.5241923999758 |
60 | PENp | 132.6 | 182.665006223793 |
61 | RNGe | 0.3 | 0.00223804164828743 |
62 | RNGe | 0.31 | 0.00260452254421197 |
63 | RNGe | 0.31 | 0.00287251561053182 |
64 | RNGe | 0.31 | 0.0030847743792478 |
65 | RNGe | 0.32 | 0.00364353433071976 |
66 | RNGe | 0.32 | 0.00377944774660896 |
67 | RNGe | 0.33 | 0.0043408657779181 |
68 | RNGe | 0.34 | 0.00502676719160926 |
69 | RNGe | 0.35 | 0.00563738328135834 |
70 | RNGe | 0.36 | 0.00628738808546234 |
71 | RNGe | 0.37 | 0.00686342271354899 |
72 | RNGe | 0.39 | 0.00779875939479639 |
73 | RNGe | 0.4 | 0.00836998638844766 |
74 | RNGe | 0.42 | 0.00921748092040848 |
75 | RNGe | 0.44 | 0.0102841822185981 |
76 | RNGe | 0.47 | 0.0118534262126143 |
77 | RNGe | 0.49 | 0.0124813303614828 |
78 | RNGe | 0.52 | 0.0139605333285567 |
79 | RNGe | 0.56 | 0.0160074061872641 |
80 | RNGe | 0.59 | 0.0166745382209565 |
81 | RNGe | 0.63 | 0.0186960844902897 |
82 | RNGe | 0.68 | 0.0213195281887486 |
83 | RNGe | 0.72 | 0.0220546233470271 |
84 | RNGe | 0.78 | 0.0257736844389772 |
85 | RNGe | 0.83 | 0.0269552797941939 |
86 | RNGe | 0.89 | 0.0284120249967939 |
87 | RNGe | 0.96 | 0.0314296505534594 |
88 | RNGe | 1.03 | 0.0329531531465774 |
89 | RNGe | 1.11 | 0.0350481850198095 |
90 | RNGe | 1.2 | 0.0374002630586924 |
91 | RNGe | 1.29 | 0.0382949636463525 |
92 | RNGe | 1.4 | 0.0421508580065854 |
93 | RNGe | 1.51 | 0.0438115216286113 |
94 | RNGe | 1.63 | 0.0455127234777333 |
95 | RNGe | 1.76 | 0.0463916606952633 |
96 | RNGe | 1.9 | 0.0473442903819639 |
97 | RNGe | 2.05 | 0.0461838400552538 |
98 | RNGe | 2.22 | 0.0470472464137365 |
99 | RNGe | 2.4 | 0.0442985944040365 |
100 | RNGe | 2.64 | 0.0517477545626182 |
101 | RNGe | 2.89 | 0.0449188061444119 |
102 | RNGe | 3.09 | 0.0350087904744153 |
103 | RNGe | 3.34 | 0.0260608153224847 |
104 | RNGe | 3.61 | 0.017575034135677 |
105 | RNGe | 3.91 | 0.011597213591902 |
106 | RNGe | 4.23 | 0.00698651925454324 |
107 | RNGe | 4.58 | 0.00420001192901242 |
108 | RNGe | 4.96 | 0.00233112868277044 |
109 | RNGe | 5.37 | 0.00109626141275523 |
110 | RNGe | 5.83 | 0.000673015773965007 |
111 | PENe | 5.96 | 0.00442463347154718 |
112 | PENe | 5.56 | 0.00780350669639281 |
113 | PENe | 5.15 | 0.0128532253416846 |
114 | PENe | 4.74 | 0.0196122475138409 |
115 | PENe | 4.32 | 0.0277375767198909 |
116 | PENe | 3.91 | 0.0378725258909174 |
117 | PENe | 3.51 | 0.0483988063193173 |
118 | PENe | 3.12 | 0.0522114541706407 |
119 | PENe | 2.76 | 0.0443042555050492 |
120 | PENe | 4.03 | 0.227510362226532 |
The contents of this table can be downloaded as a .xlsx file here.