WO2016102511A1

WO2016102511A1 - Particle detector with fast timing and high rate capability

Info

Publication number: WO2016102511A1
Application number: PCT/EP2015/080873
Authority: WO
Inventors: Marcello MAGGI; Rui de OLIVEIRA; Archana Sharma
Original assignee: Cern European Organisation For Nuclear Research
Priority date: 2014-12-23
Filing date: 2015-12-21
Publication date: 2016-06-30

Abstract

An avalanche particle detector assembly comprises, a cover resistive layer (7), a first readout layer (20) comprising a plurality of readout means and two or more detection layers (8) located between said resistive cover layer and said first readout layer (20). Each detection layer comprises a drift layer (9) and an amplification layer (10). The amplification layer (10) consists of only electrically resistive material and comprises a first dielectric layer (12), wherein the readout layer is capacitively coupled to the amplification layer of the or each detection layers.

Description

PARTICLE DETECTOR WITH FAST TIMING AND HIGH RATE CAPABILITY

The present invention relates to a gas detector for particle detection with a high detection rate and extremely fast time resolution..

There are many areas of technology where there is a need to employ a particle detector with both good time resolution and high rate capability. These areas include X-ray monitoring in plasma oscillations, neutron detection, single photon detection, small angle scattering X-ray crystallography, small animal PET scanning, radiation monitoring, medical imaging for diagnostics, time-of-flight PET scanning, UV sensitive detectors and X-ray scanners in general.

In particular, in high energy physics, calorimeters for some experiments require a time resolution of less than 100 picoseconds and a rate capability of at least around 1 MHz per cm².

Devices achieving these requirements have been provided by using microplate chambers which are coupled to a photo multiplier tube. However, such devices are expensive because of their difficulty to manufacture; they also have a relatively short working life, and can be bulky. Such technology does not therefore lend itself to many potential applications, most notably those in the medical field where cost, bulk, and portability can be significant practical factors for employment of the technology. Accordingly, there is a need to produce improved gas detector structures which meet the demanding timing and rate criteria yet which are cost effective to produce, can be produced in bulk, and have an extended lifetime when compared to current technologies. According to the present invention there is provided a particle detector assembly comprising: a cover resistive layer; a first readout layer comprising a plurality of readout means; two or more detection layers located between said resistive cover layer and said first readout layer , each detection layer consisting of only electrically resistive materials and comprising: a drift layer; and an amplification layer, wherein the amplification layer comprises one or more dielectric layers; wherein the readout layer is capacitively coupled to the amplification layer ofeach of the detection layers. With the structure of the present invention it is possible to achieve a device with high time resolution (less than 100 picoseconds) whilst ensuring a high rate capability (more than 1 MHz per cm²).

In an alternative configuration, the amplification layer may comprise a first dielectric layer and a second dielectric layer, wherein a plurality of through holes extend through the first dielectric layer. The dense electric field in the through holes results in an increased space resolution of the detector.

In a further alternative configuration, the one or more dielectric layers may be coated on both sides by first and second resistive coatings to reduce the negative effects of sparks in the detector as well as to control more precisely the resistivity of the amplification layer.

The following example of the present invention will now be described with the reference to the accompanying drawings, in which:

Figure 1 is a schematic side cross-sectional view of a particle detector assembly according to the present invention;

Figure 2 is a schematic side cross-sectional view of a particle detector assembly according to the present invention using two readout layers;

Figure 3 is a side schematic view of two detection layers that may be employed with the configuration of the present invention; and

Figure 4 is a side schematic cross-sectional view of a first example resistive layer that may be employed with the present invention.

Figure 5 is a side schematic cross-sectional view of a second example resistive layer that may be employed with the present invention. Figure 6 is a side schematic cross-sectional view of an example implementation of the present invention.

Referring to Figure 1 , an example particle detector in accordance with the present invention comprises detection layers 8 positioned between a resistive cover layer 7 and a readout layer 20. In this example two detection layers 8 are shown, although the device can be constructed withmore than two detection layers 8. . Each detection layer 8 comprises a drift layer 9, and an amplification layer 10. Each amplification layer 10 comprises a dielectric layer 12. This dielectric layer 12 may be coated on both sides by additional resistive layers to limit the effects of sparks in the detector and to control more precisely the resistivity of the dielectric layer 12. In the present invention, the electrical resistivity of the dielectric layer 12 is in the range of 1 -100 MOhm/cm².

Each drift layer 9 is formed by the space between the amplification layer 10 and the layer above, which can be either another amplification layer or the cover resistive layer. The space is obtained by placing spacing means (not shown) on the amplification layer 10. Each drift layer is filled with a gas. This gas can be any type of conventional gas used in gas detectors, such as Argon CO₂ mixtures. The materials used in the examples below are robust enough to usesecure and ecological gas mixture as well as as air.

An electrical field is established in each drift layer 9 by applying a different high voltage (HV_drift, HV_st_agei , HV_stag_e2) to the dielectric layers 12 of the different detection layers and to the dielectric layer 12 of the cover resistive layer 7. On the readout layer 20 there are formed a plurality of readout components 21 which may be in the form of metallic pads, strips or a mesh for connection to external components. The readout layer 20 is electrically connected to the ground or to a substantially lower voltage than any of the dielectric layers 12 or the cover resistive layer 7.

As a result, and because each detection layer consists of only electrically resistive material, every dielectric layer 12 is capacitively coupled to the dielectric layers 12 of adjacent amplification layers 10 as well as to the readout layer 20. This is represented by the capacitors in Figure 1. The voltage levels are typically established by a cascade of increasing voltage levels, resulting in a voltage difference between successive layers of about 1 -10 kV.

When a particle enters the detector, a number of primary ionization processes take place in the drift layer 9. The charged particles resulting from these primary ionization processes drift to the dielectric layer 12, whichresults in a change in the charge of the coupling capacitances of said dielectric Iayer12 and can thus be picked up by the readout layer through the capacitive coupling. This is represented by the signal generator in Figure 1.

Referring to Figure 2, another example particle detector in accordance with the present invention comprises detection layers 8 positioned between two readout layers 20 and 21. The second readout layer 21 on top of the detector further improves the timing and the rate of the detector, in particular when the number of detection layers increases. When the readout layers 20 and 21 are implemented as longitudinal strips, and the strips of readout layer 20 are substantially orthogonal to those of readout layer 21 , the detector can detect particles along two dimensions X and Y.

Referring to Figure 3, another example particle detector in accordance with the present invention comprises detection layers 8 positioned between a resistive cover layer 7 and a readout layer 20. For clarity, the electrical schema of the detector is omitted from Figures 3-6.

Each amplification layer comprises a first dielectric layer 12, and a second dielectric layer 13. A plurality of through holes 14 extend through the second dielectric layer 13. The dense field in the through holes 14 enables amplification in the amplification layer at much lower voltage levels than the example in Figure 1. In this example, the second dielectric layer 13 is coated on one side by a resistive material, such as DLC (Diamond-Like Carbon).

As discussed below, the materials of the respective layers are selected such that it is possible, through capacitive coupling, to extract signals through the readout layer 20 from all the detection layers 8. The materials are selected such that all the detection layers 8 are transparent to the signal to be extracted to allow plural layers to be provided. By provision of such plural layers it is possible to improve time resolution and response.

Several approaches are possible in terms of implementing the present invention and appropriate selection of construction and materials. Two examples will now be described. In both configurations there are certain core components, such as the cover resistive layer 7, readout layer 20 and readout means 21 which can be formed in a common manner and from common materials such as copper for readout means 21.

In the example in Figure 4 the detector device is provided with one or more detection layers 8 and corresponding amplification layers 10 formed with a highly resistive polyimide second dielectric layer 13 that may be formed from Apical Kaneka. In this example this dielectric layer 13 has a thickness of 100 pm. A resistive layer is formed on this second dielectric layer 13 from DLC, in this example with a thickness of 0.1 pm. The first dielectric layer 12 in this example and for each amplification layer 10 is formed from a sandwich of polyimide, again preferably Apical Kaneka, with a thickness of 22 um, the sandwiching layers being formed also by thin layers of DLC. This structure enables amplification layer 10 to be provided which is transparent to signals to be received and which has extremely good time resolution and excellent rate capabilities with minimal losses up to 10 MHz per cm² of detector area.

Figure 5 shows an alternative configuration for the amplification layer 10, in this case with the second dielectric layer 13 also being formed by Apical Kaneka at a thickness of 100 pm. Again a DLC layer of 0.1 pm is formed as resistive layer 1 1 , and the support first dielectric layer 12 in this case is formed with XC Dupont (RTM) Kapton at a thickness of 25 pm. Such Kapton material is a low resistive polyimide.

Figure 5 shows a further alternative configuration for the amplification layer 10, in this case with the second dielectric layer 13 being formed by XC Dupont Kapton at a thickness of 50 pm. A DLC layer is formed as a resistive layer 1 1. The first dielectric layer 12 is formed by XC Dupont Kapton at a thickness of 25 pm.

Figure 6 shows an example configuration of the detector which was used as proof of concept of the present invention in the laboratory. In this example, each amplification layer consists of a 50 pm layer of XC Dupont Kapton coated with a DLC layer on the top, resulting in a resistivity of 80 MOhm/cm², with through holes extending through this layer of kapton and its coating. The layer is placed on a 25 pm layer of kapton having a resistivity of 5 MOhm/cm².

In all of the above examples, the drift gap is obtained by using conventional spacers, such as spacers made from polycarbonate. The height of the drift gap is preferably 250 pm. In all of the above examples, any voltage levels can be applied to the cover resistive layer and the dielectric layers, however the field strength obtained within each drift layer is preferably 420 V / 50 pm.

In all the examples it is possible to extract, because of the transparent nature of the amplification layer 10 a readout signal during the amplification phase of operation of the device improving time resolution. As will be appreciated from above, the present invention describes particle gas detectors which are much improved over prior art configurations in terms of simplicity of construction, ease of manufacture, size and operating life. Furthermore, they provide devices with much improved operating characteristics when compared to the prior art.

Claims

1. An avalanche particle detector assembly comprising:

a cover resistive layer (7);

a first readout layer (20) comprising a plurality of readout means;

two or more detection layers (8) located between said resistive cover layer and said first readout layer (20), each detection layer comprising:

a drift layer (9); and an amplification layer (10),

wherein the amplification layer (10) consists of only electrically resistive material and comprises:

a first dielectric layer (12);

wherein the readout layer is capacitively coupled to the amplification layer of the or each detection layers.

2. An avalanche particle detector assembly in accordance with claim 1 , wherein the amplification layer comprises a second dielectric layer (13)

and a plurality of through holes (14) extending through the second dielectric layer (13) to the first dielectric layer (12).

3. An avalanche particle detector assembly in accordance with claim 1 or 2, wherein the first dielectric layer (12) is coated by a resistive layer (1 1 ).

4. An avalanche particle detector assembly in accordance with claim 2, wherein the second dielectric layer (12) is coated by a resistive layer (1 1 ).

5. An avalanche particle detector in accordance with any preceding claim, comprising a second readout layer (21 ), and wherein the one or more detection layers are located between said first and second readout layers.

6. An avalanche particle detector in accordance with any preceding clai wherein the one or more readout means are readout pads or readout strips.

7. An avalanche particle detector assembly in accordance with any preceding claim, wherein the or each dielectric layer (12) consists of resistive bulk material.

8. An avalanche particle detector assembly in accordance with claim 7, wherein the resistive bulk material is Kapton.

9. An avalanche particle detector assembly in accordance with claims 1 to 6, wherein the or each dielectric layer (12) is coated on both sides respectively by a first and second resistive coating.

10. An avalanche particle detector assembly in accordance with claim 9, wherein the dielectric material for the or each dielectric layer (12) is kaneka, and the first and second resistive coating is DLC.