According to r=mvBq, the ratio of the orbital radius of charged particles after 1 and the second pass through the slit between two D boxes is r 1: R2 = 1: 2, so A is correct.
B, the particle is accelerated once by the electric field, and the kinetic energy increases qU,
Then the number of times the particle is accelerated n=EKMqU=qB2R22mU.
The number of times a particle moves in a magnetic field n'= N2 = qb2r 24 mu.
T=2πmBq
Then the time required for a particle to reach the exit from rest is t = n't =πbr22u, so b is correct.
C, according to qvB=mv2R, know that v=qBRm,
The kinetic energy of charged particles leaving the cyclotron is ek = 12mv2 = B2Q2 R22m, so CD is wrong.
So: ab.