BSMA

55. 5

55

Filter step 3.5 sheet 0.5, gap 3.0

10 1060 80 35 55 25

Condenser width 260, HV electrode thickness 3.0Collector size 32.4×170.6, gap 1.3

C0

R1

R2

E

C4

C1

C2

C3

V

Plain IGMA

Aerosol inlet

b d

a

h

h

u

E

Sheath air inlet

Aerosoloutlet

Ballast air(could be recirculated to sheath

air)

V

The ions in the outlet are collected by a well-insulated and shielded electrostatic filter powered by an internal battery and DC-DC converter. The collector is connected to the ground through an electrometric amplifier. Electrostatic shielding from the high voltage deflector grid allows free manipulation with mobility control voltage.

step 12.5 mm

gap 20 mm

gap 2 + 18 mm

The deflector grid is connected to a RC circuit with a time constant of about 4 s. The capacitor of this circuit is quickly charged up to 6 kV and slowly discharged through the resistor with a period of 20 s. This assures the logarithmical scanning of mobility from the lowest to the highest value of the mobility range during the 20 s period.

Modified IGMA

TRAJECTORIES OF IONS IN A MODIFIED IGMA

0

2

4

6

8

10

0 2 4 6 8 10 12 14 16 18Particle regime fraction number

Fra

ctio

n n

ois

e c

m-3

3 min time resolution

15 min time resolution

10

20

30

Noise : cm–3

Mobility : cm2V−1s−1

00.03 0.1 1 3

wintertime outdoor air, rime and light snowfall

closed room,rich in radon

IGMABSMA

0.03 cm2V−1s−1 Mobility 3 cm2V−1s−1

NOISE

0

2

4

6

8

10

12

0 3 6 9 12 15 18 21Time : hour

No

ise

: cm

-3

Fan on Fan off

BSMA

ACCUMULATION AND DECAY OF RADON DAUGHTERS