3.6.35 · D1Radiation effects — TID, SEE, displacement damage
Intuition Is poore topic ke peeche ek hi idea haiSpace mein chote-chote tez bullets (particles) bhari padi hain jo tumhare satellite ki electronics mein ghus jaati hain aur jahan rukti hain wahan energy dump karti hain. Woh dumped energy ya toh ek signal ko scramble karti hai, ya kisi transistor ke behave karne ka tarika shift karti hai, ya phir crystal ko physically tod deti hai — aur poora subject bas un teen outcomes ke teen naam hai.
Parent note ko bina atke padhne ke liye tumhe pehle bullets aur target ki vocabulary chahiye. Yeh page har symbol ko scratch se build karta hai. Hum koi bhi letter use nahi karte jab tak uski picture nahi bana lete.
Sab kuch shuru hota hai ek tez particle se jo ek solid material mein ghusta hai. Socho ek marble jise saaf jelly ke slab mein fire kiya gaya ho.
Matter ka ek chota tukda jo tezi se move karta hai: ek electron , ek proton , ya ek heavy ion (poora atomic nucleus, jaise iron, electrons se stripped). "Tez" matlab iske paas kinetic energy hai — motion ki energy.
Definition Material / targetWoh solid jisme particle ghusta hai. Electronics mein yeh zyaadatar silicon (Si, semiconductor) aur silicon dioxide (SiO₂, woh glassy insulator jo uske upar baith'ta hai) hota hai.
Humein dono kyun chahiye: radiation ke effects hamesha ek baat-cheet hote hain jo andar ghusta hai aur jo use hit karta hai ke beech. Koi ek badlo aur damage badal jaata hai.
Definition Energy — electron-volts (eV) mein measure ki jaati haiEnergy particle ka "kitna punch" hai. Hum ise electron-volts mein measure karte hain: 1 eV 1 volt 1 keV = 1 0 3 eV 1 MeV = 1 0 6 eV
Picture: ek bada, tez marble = zyaada eV. Space proton aksar "1 MeV
Har E alag "kiska energy?" sawaal ka jawab deta hai — isliye unke saath subscripts lagte hain.
Ek tez particle un atoms ke electrons ko drag karta hai jis se guzarta hai, kuch ko loose kar deta hai. Har free hua electron ek "hole" chod jaata hai — ek khali jagah jo positive charge ki tarah behave karti hai.
Definition Ionization aur electron–hole pairIonization = electron ko loose karna. Freed electron (negative) aur uska choda hua hole (positive) milke ek electron–hole pair hai. Yeh TID aur SEE ka core event hai.
E pair 3.6 eV 18 eV E deposited E deposited / E pair
Humein yeh kyun chahiye: yeh "peeche chodi gayi energy" aur "create hue charge" ke beech exchange rate hai — physics se circuit trouble tak ka bridge.
Definition Electric charge —q Charge woh electrical "stuff" hai jo electrons aur holes carry karte hain. Sabse chota chunk q = 1.6 × 1 0 − 19 C pico-coulombs 1 pC = 1 0 − 12 C femto-coulombs 1 fC = 1 0 − 15 C
Ek particle apni saari energy ek jagah dump nahi karta — woh ek trail chod'ta hai, apne path ke saath step by step energy khoota rehta hai.
d x d E d x d E path ke saath loss ki rate hai. Agar tumhe har jagah loss-per-step pata hai, toh saare steps ko add karne se total milta hai:
E deposited = ∫ d x d E d s
∫ har jagah same ho. Yeh usually nahi hota — particle slow hota jaata hai, isliye uska loss-per-step track ke saath badalta rehta hai. Symbol ∫ andar chodi gayi total energy = saari choti losses ka sum. Koi doosra tool iska jawab nahi deta.
Definition LET — Linear Energy TransferLET d x d E ρ MeV ⋅ cm 2 / mg
ρ g/cm 3 ρ = 2.33 g/cm 3
Ek bullet ek event hai. Ek mission saalon mein trillions bullets hai. Dheere-dheere ike pile-up describe karne ke liye hum dose measure karte hain.
D rate D rate per day hai. Running total Total Ionizing Dose hai:
TID ( t ) = ∫ 0 t D rate ( t ′ ) d t ′
cumulative hai; LET per-event hai
Inhe mix mat karo. LET batata hai ek particle kitna bura hai (SEE). Dose/TID batata hai poore mission mein kitna pile up hua (TID). Alag sawaal, alag symbols.
TID aur SEE dono ek MOSFET naam ke switch par attack karte hain. Tumhe uske teen numbers chahiye.
Definition Threshold voltageV th V th voltage hai jo tumhe apply karni padti hai jab tak woh on nahi ho jaata . Radiation se trapped charge is on-point ko shift karta hai; hum shift ko Δ V th Δ
Definition Oxide capacitanceC ox capacitor do conductors hain jiske beech insulator hai — yeh charge store karta hai. Uski capacitance C Q Q = C V t ox ϵ ox C ox = t ox ϵ ox C ox Δ V th = − Q trap / C ox
Definition Critical chargeQ crit sabse chota charge jo ek single particle ko stored bit flip karne ke liye dump karna padta hai: Q crit = C node ⋅ V crit C node
Yeh predict karne ke liye ki errors kitni baar hoti hain humein "kitne particles, kitna bada target" ki language chahiye.
Φ Flux = har unit time mein ek square centimetre cross karne wale particles ki sankhya. Socho barish: flux raindrops per second hai jo zameen ke ek fixed patch par girte hain. Φ ( LET )
σ effective target area , cm 2 / bit hit rate milti hai:
R = σ ⋅ Φ
Intuition "Cross-section" kyun, sirf "area" kyun nahi?Asli transistor ke fuzzy edges hote hain — kuch hits use flip karte hain, kuch nahi, angle aur LET par depend karta hai. σ equivalent perfectly-sharp bullseye hai jo observed error rate reproduce karta hai. Yeh ek measured number hai, ruler measurement nahi.
Teesra mechanism alag hai: kabhi-kabhi bullet ek atomic nucleus se seedha takraa'ta hai aur poore atom ko uski lattice spot se knock out kar deta hai.
Definition Crystal lattice aur displacementLattice = silicon atoms ki woh neat repeating grid, jaise ek crate mein stack kiye hue santre. Ek displacement = ek santra apni slot se punch hoke nikal jaata hai, ek gap aur kahin ek loose santra chod'ta hai. Yeh defects charges trap karte hain aur dheere-dheere device barbaad kar dete hain (yahi Displacement Damage hai).
E recoil M p , M Si M p M Si E recoil θ
Ionization: electron-hole pairs
Nuclear collision: recoil
Flux Phi and cross-section sigma
Vault mein yeh kahan hain: woh orbit jo Φ D rate Spacecraft Orbits aur Van Allen Belts se aata hai; woh levels kaise badhte aur ghatte hain Solar Activity Cycles se aata hai; V th C ox Semiconductor Physics mein hai; upsets ka fix Error Correcting Codes mein hai; mission-level risk maths Reliability Engineering mein hai; power-side effects Photovoltaic Systems aur Power Budget ko touch karte hain. Yeh sab wapas parent mein feed hota hai, main radiation-effects note .
Jawab chhupao, zyaad se bol ke dekho, phir reveal karo.
Ek electron-volt (eV) physically kya matlab hai? Woh energy jo ek electron 1-volt ke difference ko cross karne par gain karta hai; 1 MeV = 1 0 6 eV
Electron–hole pair kya hota hai? Ek freed electron (−) aur uske peeche choda gaya positive "hole"; ionization se banta hai.
Deposited energy E deposited Roughly E deposited / E pair E pair ≈ 3.6 eV
d x d E Particle ke track ke saath distance ke ek chote step mein khoi gayi energy.
E deposited Kyunki loss-per-step change hota hai jab particle slow hota hai, isliye tumhe kai chote slices sum karne padte hain.
LET kya hai aur uski unit kya hai? Linear Energy Transfer, d x d E MeV ⋅ cm 2 / mg
Dose kya hai, aur rad vs Gray? Per kilogram material mein deposited ionizing energy; 1 Gy = 1 J/kg 1 rad = 0.01 Gy
V th MOSFET on karne ke liye zaroori voltage; radiation ise Δ V th
Q crit Woh minimum charge jo stored bit flip karta hai, Q crit = C node V crit
Flux Φ σ Error/hit rate R = σ Φ
LET aur dose mein kya difference hai? LET = per-single-particle severity (SEE); dose/TID = mission-total pile-up (TID).
Displacement damage atomic level par kya hota hai? Ek nucleus crystal lattice se knock out ho jaata hai, defects chod'ta hai jo carriers trap karte hain.