Specification for the ZP1221/01 Geiger Muller tube
Source: environment.data.gov.uk (2024-01-03)

BEIS: Ambient gamma radiation dose rates across the UK. Data received from 96 fixed and mobile monitors measuring the ambient (background) gamma radiation dose rate across the UK on an hourly basis.
Background radiation continues to be the main component of observed levels of gamma radiation recorded at sites. The observed UK annual radiation dose rate ranges from around 0.5 mSv to 1.0 mSv with an average of less than 0.7mSv.
High readings

Future data now published under DESNZ
The higher readings, identified by red type in the ‘Max’ column of these files, are at a level which requires investigation. Each has been investigated and no specific reason found.
It is not unusual to have a small number of slightly elevated readings, often referred to as anomalies, which could be due to weather or power related factors, though the cause is often unknown. As no fault or reason was found, there is no justification for amending the readings on the database.

ZP1221

ZP1221/01

GEIGER MULLER TUBE

Halogen-quenched y radiation counter tube. The ZP 1221/01 is the low background version of the ZP1221.

QUICK REFERENCE DATA
Dose rate range

Plateau threshold voltage
Plateau length
Recommended supply voltage
Chrome iron cathode

2x 10*to 3
2x105to 3x 10"
400

100

450

525

mGy/h
R/h

V

V

Vv
mg/cm?

This data must be read in conjunction with General Information Geiger Miiller tubes.

MECHANICAL DATA Dimensions in mm
Figure 1
metal cap polyolefin sheath cathode - tinned
braided copper wire
oo)?
28 _ . —
© nax 3 C
anode - plain
braided copper wire

20 __.I al

18 9

a ><. sensitive length ————————» ° i

oe _— 100 a

MBB666 Note: tube must not be clamped within 30 mm of either end.
CATHODE (ZP1220)
Thickness 525 mg/cm?
Sensitive length 240 mm
Material chrome iron
ENVIRONMENTAL (Manufacturer's test conditions)
Shock (half sine wave 3 ms duration) - peak acceleration 392 mis?
FILLING neon, argon, halogen
CAPACITANCE
Anode to cathode 10 pF
TUBE WEIGHT 350 g

ZP1221

ZP1221/01
OPERATING CHARACTERISTICS (Ambient temperature ~ 25 °C)
Measured in circuit of Figure 2.
Starting voltage max 350 Vv
Plateau threshold voltage max 400 Vv
Plateau length 100 Vv
Recommended supply voltage 450 Vv
Plateau slope max 0.15 KIN
Background (shielded with 50 mm Pb with .
an inner liner of 3 mm Al), at ZP1221: max 90 count/min
recommended supply voltage ZP1221/01: max 60 count/min
Dead time, at recommended supply voltage max 210 us
LIMITING VALUES (Absolute max. rating system)
Anode resistor min 2.7 MQ
Anode voltage max 500 Vv
Ambient temperature
- continuous operating max +70 °C
min - 40 °C
- storage max +75 °C
LIFE EXPECTANCY
Life expectancy at = 25 °C 5 x 10'° count
MEASURING CIRCUIT
™, 2.7MQ
330pF
fe output
2.7MQ
D7678
+V supply

Figure 2

ZP1221
ZP1221/01

M2250
i ——— mut:

count/s [|_|

104

103

102

Saliliras

“Ht aii

107 10

Typical counting rate as a function of dose rate (137Cs)

ZP1221

2P1221/01

102 mGy/h_ 103

Typical current as a function of dose rate (137Cs)

as
Z Tee
EERE 7
t C tt |
q = r
[| | |
tt +
I |
TPT +
at |

relative
response

energy (keV)

Typical energy response relative to !37Cs,

ZP1221
ZP1221/01

Typical polar responses (norma

ised to 100% at 0°).